Electron Donor Systems to Facilitate Development of Assays for Two Flavoproteins Involved in Tetrahydromethanopterin Biosynthesis

Methane production by archaea depends on tetrahydromethanopterin (H4MPT), a pterin-containing cofactor that carries one-carbon units. Two redox reactions within the nine steps of H4MPT side chain biosynthesis have been hypothesized. Biochemical assays have demonstrated that the archaeal iron-sulfur flavoprotein dihydromethanopterin reductase X (DmrX or MM1854) catalyzes the final reaction of the pathway, the reduction of dihydromethanopterin to H4MPT, using dithiothreitol (DTT) as an artificial electron donor. The crystal structure of DmrB, a bacterial DmrX homolog that lacks iron-sulfur clusters, has led to a proposed ping-pong mechanism of electron transfer between FMNH2 and the FMN prosthetic group of DmrB. However, an enzymatic assay to test the hypothetical DmrB mechanism is lacking because a suitable electron donor has not previously been identified. Furthermore, a second uncharacterized archaeal flavoprotein (MM1853) has been hypothesized to function in H4MPT side chain biosynthesis. In this work, to facilitate the development of assays to elucidate the functions of DmrB and MM1853, we tested a variety of electron donors, including dithiothreitol, ferredoxin, and a system consisting of NADH and an NADH-dependent flavin-reducing enzyme (Fre). Reduction of the DmrB prosthetic group (FMN) was measured as a decrease in absorbance at 460 nm. NADPH, NADH, and DTT were unable to reduce DmrB. However, NADH/Fre was able to reduce DmrB within 70 min (initial rate of 1.3 μM/min), providing the basis for a future DmrB activity assay. Carbon monoxide (CO)/CO dehydrogenase/ferredoxin reduced DmrB more rapidly within 6 min. Both electron transfer systems reduced a second flavin-containing archaeal protein MM1853, which is predicted to catalyze the third step of H4MPT biosynthesis. While NADH and NADPH were incapable of directly reducing the FMN cofactor of MM1853, DTT or NADH/Fre could eliminate the FMN peaks. These results establish the basis for new oxidoreductase assays that will facilitate testing several proposed DmrB mechanisms and defining the specific function of MM1853 in methanogen cofactor biosynthesis.

Optical redox imaging of ANT1-de-cient muscles

Adenine nucleotide translocator(ANT)is a mitochondrial protein involved in the exchange of ADP and ATP across the mitochondrial inner membrane.It plays a crucial role in cellular energy metabolism by facilitating the transport of ATP synthesized within the mitochondria to the cytoplasm.The isoform ANT1 predominately expresses in cardiac and skeletal muscles.Mutations or dysregulation in ANT1 have been implicated in various mitochondrial disorders and neuromuscular diseases.We aimed to examine whether ANT1 deletion may affect mitochondrial redox state in our established ANT1-de-cient mice.Hearts and quadriceps resected from age-matched wild type(WT)and ANT1-de-cient mice were snap-frozen in liquid nitrogen.The Chance redox scanner was utilized to perform 3D optical redox imaging.Each sample underwent scanning across 3–5 sections.Global averaging analysis showed no signi-cant differences in the redox indices(NADH,flavin adenine dinucleotide containing-flavoproteins Fp,and the redox ratio Fp/(NADH+Fp)between WT and ANT1-de-cient groups.However,quadriceps had higher Fp than hearts in both groups(p¼0:0004 and 0.01,respectively).Furthermore,the quadriceps were also more oxidized(a higher redox ratio)than hearts in WT group(p¼0:004).NADH levels were similar in all cases.Our data suggest that under non-stressful physical condition,the ANT1-de-cient muscle cells were in the same mitochondrial state as WT ones and that the signi-cant difference in the mitochondrial redox state between quadriceps and hearts found in WT might be diminished in ANT1-de-cient ones.Redox imaging of muscles under physical stress can be conducted in future.

Covalent flavoproteins:types,occurrence,biogenesis and catalytic mechanisms

Flavoproteins are proteins that contain a nucleic acid derivative of riboflavin:flavin adenine dinucleotide(FAD)or flavin mononucleotide(FMN).Flavoproteins are involved in a wide array of biological processes,such as photosynthesis,DNA repair and natural product biosynthesis.It should be noted that 5%-10%of flavoproteins have a covalently linked flavin prosthetic group.Such covalent linkages benefit the holoenzyme in several ways including improving the stability and catalytic potency.During the past decade,significant progress has been made in covalent flavoproteins,especially with respect to enzyme-dependent biogenesis and discovery of novel linkage types.The present review gives a condensed overview of investigations published from March 2009 to December 2021,with emphasis on the discovery,biogenesis and their catalytic role in natural product biosynthesis.

3D imaging of the mitochondrial redox state of rathearts under normal and fasting conditions

The heart requires continuous ATP availability that is generated in the mitochondria.Althoughstudies using the cell culture and perfiused organ models have been carried out to investigate thebiochemistry in the mitochondria in response to a change in substrate supply,mitochondrialbioenergetics of heart under normal feed or fasting conditions has not been studied at the tissuelevel with a sub-millimeter spatial resolution either in vivo or er vivo.Oxidation of many food-derived metabolites to generate ATP in the mitochondria is realized through the NADH/NAD+couple acting as a central electron carrier.We employed the Chance redox scanner thelow-temperat ure fluorescence scanner to image the three-dimensional(3D)spatial distribution of themitochondrial redox states in heart tissues of rats under normai feeding or an overnight star-vation for 14.5 h.Multiple consecutive sections of each heart were imaged to map three redoxindices,i.e,NADH,oxidized favoproteins Fp,including flavin adenine dinucleotide(FAD)andthe redox ratio NADH/Fp.The imaging results revealed the micro-heterogeneity and the spatial distribution of these redox indices.The quantitative analysis showed that in the fasted hearts thestandard deviation of both NADH and Fp,ie.,SD NADH and SDFp,significantly decreasedwith a p value of 0.032 and 0.045,respectively,indicating that the hearts become relatively morehomogeneous after fasting.The fasted hearts contained 28.6%less NADH(p=0.038).No sig.nificant change in Fp was foumnd(p=0.4).The NADH/Fp ratio decreased with a marginalP value(0.076).The decreased NADH im the fasted hearts is consistent with the cardiac celsreliance of fatty acids consumption for energy metabolism when glucose becomes scarce.Theexperimental o bservation of N ADH decrease induced by dietary restriction in the heart at tissuelevel has not been reported to our best knowledge.The Chance redox scanner demonstrated thefeasibility of 3D imaging of the mitochondrial redox st ate in the heart and provides a usefil toolto study heart metabolism and fiunction under normal,dietary-change and pathological con-ditions at tisue level. We would like to thank Dr.Joseph Baur for thehelpful discussion and Dr.Hui Qiao for animalpreparation and organ harvesting.

IMAGING REDOX STATE HETEROGENEITY WITHIN INDIVIDUAL EMBRYONIC STEM CELL COLONIES

Redox state mediates embryonic stem cell(ESC)differentiation and thus offers an important complementary approach to understanding the pluripotency of stem cells.NADH redox ratio(NADH/(Fp t NADH)),where NADH is the reduced form of nicotinamide adenine dinucleotide and Fp is the oxidizedflavoproteins,has been established as a sensitive indicator of mitochondrial redox state.In this paper,we report our redox imaging data on the mitochondrial redox state of mouse ESC(mESC)colonies and the implications thereof.The low-temperature NADH/Fp redox scanner was employed to image mESC colonies grown on a feeder layer of gamma-irradiated mouse embryonicfibroblasts(MEFs)on glass cover slips.The result showed significant heterogeneity in the mitochondrial redox state within individual mESC colonies(size:~200-440μm),exhibiting a core with a more reduced state than the periphery.This more reduced state positively correlates with the expression pattern of Oct4,a well-established marker of pluripotency.Our observation is thefirst to show the heterogeneity in the mitochondrial redox state within a mESC colony,suggesting that mitochondrial redox state should be further investigated as a potential new biomarker for the stemness of embryonic stem cells.

PROBING THE IMPACT OF GAMMA-IRRADIATION ON THE METABOLIC STATE OF NEURAL STEM AND PRECURSOR CELLS USING DUAL-WAVELENGTH INTRINSIC SIGNAL TWO-PHOTON EXCITED FLUORESCENCE

Two-photon excitedfluorescence(TPEF)spectroscopy and imaging were used to investigate the effects of gamma-irradiation on neural stem and precursor cells(NSPCs).While the observed signal from reduced nicotinamide adenine dinucleotide(NADH)was localized to the mitochondria,the signal typically associated with oxidizedflavoproteins(Fp)was distributed diffusely throughout the cell.The measured TPEF emission and excitation spectra were similar to the established spectra of NAD(P)H and Fp.Fpfluorescence intensity was markedly increased by addition of the electron transport chain(ETC)modulator menadione to the medium,along with a concomitant decrease in the NAD(P)H signal.Three-dimensional(3D)neurospheres were imaged to obtain the cellular metabolic index(CMI),calculated as the ratio of Fp to NAD(P)Hfluorescence intensity.Radiation effects were found to differ between low-dose(
50 cGy)and high-dose(50 cGy)exposures.Low-dose irradiation caused a marked drop in CMI values accompanied by increased cellular proliferation.At higher doses,both NAD(P)H and Fp signals increased,leading to an overall elevation in CMI values.Thesefindings underscore the complex relationship between radiation dose,metabolic state,and proliferation status in NSPCs and highlight the ability of TPEF spectroscopy and imaging to characterize metabolism in 3D spheroids.

Relationship between Renalase Expression and Kidney Disease： an Observational Study in 72 Patients Undergoing Renal Biopsy

The relationship between the levels of renalase and changes in proteinuria, hypertension, renal function, renal tubular epithelial cell apoptosis and B-cell lymphoma-2 （Bcl-2） expression was investigated in patients （chronic nephritis, primary nephrotic syndrome or other kidney disease） that underwent renal biopsy. The study group comprised 72 patients undergoing renal biopsy. Patient profiles and renal function were collected. Concentrations of renalase and Bcl-2 were measured by immunohistochemistry. Tubular injury was detected by periodic acid Schiff staining （PAS） and renal tubular epithelial cell apoptosis was assessed by TUNEL assay. The expression of renalase was significantly lower in renal biopsy specimens than in normal kidney tissues. There was a positive linear relationship between renalase and some serum and cardiac indices; a negative correlation was found between age, eGFR, Ccr and 24-h urinary protein. Renal tubule injury index and tubular epithelial cell apoptosis index showed a negative linear correlation with renalase. The results showed that renalase probably increased the expression of Bel-2. By two independent samples t-test, renalase levels were significantly increased in the non-hypertension group than in the hypertension group. One-way ANOVA showed that renalase expression was higher in samples with Lee＇s grade Ⅲ than in those with Lee＇s grade V. The expression of renalase was significantly decreased in patients who underwent renal biopsy, and was also associated with blood and renal function. The research proved that renalase may reduce renal tubular injury and apoptosis of renal tubular epithelial cells through the mitochondrial apoptosis pathway, finally achieving the purpose of delaying the progress of renal failure.

MITOCHONDRIAL REDOX IMAGING FOR CANCER DIAGNOSTIC AND THERAPEUTIC STUDIES

Mitochondrial redox states provide important information about energy-linked biological processes and signaling events in tissues for various disease phenotypes including cancer.The redox scanning method developed at the Chance laboratory about 30 years ago has allowed 3D highresolution(∼50×50×10µm^(3))imaging of mitochondrial redox state in tissue on the basis of the fluorescence of NADH(reduced nicotinamide adenine dinucleotide)and Fp(oxidized flavoproteins including flavin adenine dinucleotide,i.e.,FAD).In this review,we illustrate its basic principles,recent technical developments,and biomedical applications to cancer diagnostic and therapeutic studies in small animal models.Recently developed calibration procedures for the redox imaging using reference standards allow quantification of nominal NADH and Fp concentrations,and the concentration-based redox ratios,e.g.,Fp/(Fp+NADH)and NADH/(Fp+NADH)in tissues.This calibration facilitates the comparison of redox imaging results acquired for different metabolic states at different times and/or with different instrumental settings.A redox imager using a CCD detector has been developed to acquire 3D images faster and with a higher in-plane resolution down to 10µm.Ex vivo imaging and in vivo imaging of tissue mitochondrial redox status have been demonstrated with the CCD imager.Applications of tissue redox imaging in small animal cancer models include metabolic imaging of glioma and myc-induced mouse mammary tumors,predicting the metastatic potentials of human melanoma and breast cancer mouse xenografts,differentiating precancerous and normal tissues,and monitoring the tumor treatment response to photodynamic therapy.Possible future directions for the development of redox imaging are also discussed.

QUANTITATIVE REDOX SCANNING OF TISSUE SAMPLES USING A CALIBRATION PROCEDURE

The fluorescence properties of reduced nicotinamide adenine dinucleotide(NADH)and oxidizedflavoproteins(Fp)including flavin adenine dinucleotide(FAD)in the respiratory chain are sensitive indicators of intracellular metabolic states and have been applied to the studies of mitochondrial function with energy-linked processes.The redox scanner,a three-dimensional(3D)low temperature imager previously developed by Chance et al.,measures the in vivo metabolicproperties of tissue samples by acquiring fluorescence images of NADH and Fp.The redox ratios,i.e.Fp/(Fp+NADH)and NADH/(Fp+NADH),provided a sensitive index of the mitochondrialredox state and were determined based on relative signal intensity ratios.Here we report thefurther development of the redox scanning technique by using a calibration method to quantifythe nominal concentration of the fluorophores in tissues.The redox scanner exhibited very goodlinear response in the range of NADH concentration between 165–1318µM and Fp between90–720µM using snap-frozen solution standards.Tissue samples such as human tumor mousexenografts and various mouse organs were redox-scanned together with adjacent NADH and Fpstandards of known concentration at liquid nitrogen temperature.The nominal NADH and Fpconcentrations as well as the redox ratios in the tissue samples were quantified by normalizing the tissue NADH and Fp fluorescence signal to that of the snap-frozen solution standards.This calibration procedure allows comparing redox images obtained at different time,independent of instrument settings.The quantitative multi-slice redox images revealed heterogeneity inmitochondrial redox state in the tissues.

CPEB1,a novel risk gene in recent-onset schizophrenia,contributes to mitochondrial complex I defect caused by a defective provirus ERVWE1

BACKGROUND Schizophrenia afflicts 1%of the world population.Clinical studies suggest that schizophrenia patients may have an imbalance of mitochondrial energy metabolism via inhibition of mitochondrial complex I activity.Moreover,recent studies have shown that ERVWE1 is also a risk factor for schizophrenia.Nevertheless,there is no available literature concerning the relationship between complex I deficits and ERVWE1 in schizophrenia.Identifying risk factors and blood-based biomarkers for schizophrenia may provide new guidelines for early interventions and prevention programs.AIM To address novel potential risk factors and the underlying mechanisms of mitochondrial complex I deficiency caused by ERVWE1 in schizophrenia.METHODS Quantitative polymerase chain reaction(qPCR)and enzyme-linked immunosorbent assay were used to detect differentially expressed risk factors in blood samples.Clinical statistical analyses were performed by median analyses and Mann-Whitney U analyses.Spearman’s rank correlation was applied to examine the correlation between different risk factors in blood samples.qPCR,western blot analysis,and luciferase assay were performed to confirm the relationship among ERVWE1,cytoplasmic polyadenylation element-binding protein 1(CPEB1),NADH dehydrogenase ubiquinone flavoprotein 2(NDUFV2),and NDUFV2 pseudogene(NDUFV2P1).The complex I enzyme activity microplate assay was carried out to evaluate the complex I activity induced by ERVWE1.RESULTS Herein,we reported decreasing levels of CPEB1 and NDUFV2 in schizophrenia patients.Further studies showed that ERVWE1 was negatively correlated with CPEB1 and NDUFV2 in schizophrenia.Moreover,NDUFV2P1 was increased and demonstrated a significant positive correlation with ERVWE1 and a negative correlation with NDUFV2 in schizophrenia.In vitro experiments disclosed that ERVWE1 suppressed NDUFV2 expression and promoter activity by increasing NDUFV2P1 level.The luciferase assay revealed that ERVWE1 could enhance the promoter activity of NDUFV2P1.Additionally,ERVWE1 downregulated the expression of CPEB1 by suppressing the promoter activity,and the 400 base pair sequence at the 3′terminus of the promoter was the minimum sequence required.Advanced studies showed that CPEB1 participated in regulating the NDUFV2P1/NDUFV2 axis mediated by ERVWE1.Finally,we found that ERVWE1 inhibited complex I activity in SH-SY5Y cells via the CPEB1/NDUFV2P1/NDUFV2 signaling pathway.CONCLUSION In conclusion,CPEB1 and NDUFV2 might be novel potential blood-based biomarkers and pathogenic factors in schizophrenia.Our findings also reveal a novel mechanism of ERVWE1 in the etiology of schizophrenia.

This research was supported by E.U.FP6 Integrated Project“Molecular Imaging”LSHG-CT-2003-503259 and E.U.FP7 Collaborative Project“FMT-XCT”.R.F.acknowledges support from the Marie Curie Program EST-MolecImag Early Stage Training MEST-CT-2004-007643.

We have imaged mitochondrial oxidation-reduction states by taking a ratio of mitochondrial fluorophores:NADH(reduced nicotinamide adenine dinucleotide)to Fp(oxidized flavoprotein).Although NADH has been investigated for tissue metabolic state in cancer and in oxygen deprived tissues,it alone is not an adequate measure of mitochondrial metabolic state since the NADH signal is altered by dependence on the number of mitochondria and by blood absorption.The redox ratio,NADH/(Fp+NADH),gives a more accurate measure of steady-state tissue metabolism since it is less dependent on mitochondrial number and it compensates effectively for hemodynamic changes.This ratio provides important diagnostic information in living tissues.In this study,the emitted fluorescence of mouse colon in situ is passed through an emission filter wheel and imaged on a CCD camera.Redox ratio images of the healthy and hypoxic mouse intestines clearly showed significant differences.Furthermore,the corrected redox ratio indicated an increase from an average value of 0.51±0.10 in the healthy state to 0.92±0.03 in dead tissue due to severe ischemia(N=5).We show that the CCD imaging system is capable of displaying the metabolic differences in normal and ischemic tissues as well as quantifying the redox ratio in vivo as a marker of these changes.

KillerRed protein based in vivo photodynamic therapy and corresponding tumor metabolic imaging

Photodynamic therapy(PDT)gains wide attention as a useful therapeutic method for cancer.It is mediated by the oxygen and photosensitizer under the specific light irradiation to produce the reactive oxygen species(ROS),which induce cellular toxicity and regulate the redox potential in tumor cells.Nowadays,genetic photosensitizers of low toxicity and easy production are required to be developed.KillerRed,a unique red fluorescent protein exhibiting excellent phototoxic properties,has the potential to act as a photosensitizer in the application of tumor PDT.Meantime,the course of tumor redox metabolism during this treatment was rarely investigated so far.Thus here,we investigated the effects of KillerRed-based PDT on tumor growth in vivo and examined the subsequent tumor metabolic states including the changes of nicotinamide adenine dinucleotide hydrogen(NADH)and flavoprotein(Fp),two important metabolic coenzymes of tumor cells.Results showed the tumor growth had been significantly inhibited by KillerRedbased PDT treatment compared to control groups.A home-made cryo-imaging redox scanner was used to measure intrinsic fluorescence and exogenous KillerRed fluorescence signals in tumors.The Fp signal was elevated by nearly 4.5-fold,while the NADH signal decreased by 66%after light irradiation,indicating that Fp and NADH were oxidized in the course of KillerRedbased PDT.Furthermore,we also observed correlation between the fluorescence distribution of KillerRed and NADH.It suggests that the KillerRed protein based PDT might provide a new approach for tumor therapy accompanied by altering tumor metabolism.

CHOP THER APY INDUCED MITOCHONDRIAL REDOX STATE ALTERATION IN NON-HODGKIN'S LYMPHOMA XENOGRAFTS

We are interested in investigating whether cancer therapy may alter the mitochondrial redox state in cancer cells to inhibit their growth and survival.The redox state can be imaged by the redox scanner that collects the fuorescence signals from both the oxidized-fAavoproteins(Fp)and the reduced form of nicotinamide adenine dinucleotide(NADH)in snap frozen tissues and has been previously employed to study tumor aggressiveness and treatment responses.Here,with the redox scanner we investigated the effects of chemotherapy on mouse xenografts of a human diffuse large B.cell lymphoma cell line(DLCL2).The mice were treated with CHOP therapy,i.e,cyclophosphamide(C)+hydroxydoxorubicin(H)+Oncovin(O)+prednisone(P)with CHO administration on day 1 and prednisone administration on days 1-5.The Fp content of the treated group was significantly decreased(p=0.033)on day 5,and the mitochondrial redox state of the treated group was slightly more reduced than that of the control group(p=0.048).The decrease of the Fp heterogeneity(measured by the mean st andard deviation)had a border-line statistical significance(p=0.071).The result suggests that the mitochondrial metabolism of lymphoma cells was slightly suppressed and the lymphomas became less aggressive after the CHOP therapy.

Cholesterol Oxidase and Its Applications

Cholesterol oxidase (COX), a bi-functional FAD-containing microbial enzyme belongs to the family oxidoreductases. COX catalyses the oxidation of cholesterol into 4-cholesten-3-one. In recent time, cholesterol oxidase has received great attention due to its wider use in clinical (determination of serum cholesterol) laboratories practice and in the biocatalysis for the production of a number of steroids. COX has been shown to possess potent insecticidal activity, besides its use to track cell cholesterol. Moreover, COX is also implicated in the manifestation of some of the diseases of bacterial (tuberculosis), viral (HIV) and non-viral prion origin (Alzheimer's). These applications and disease mechanisms have promoted the need of screening, isolation and characterization of newer microbes from diverse habitats as a source of COX to learn more about its structural and functional aspects. In this review, we discuss microbial sources of COX, its structure and important biochemical properties besides its broad range of biological functions and applications.

Clinical and muscle magnetic resonance image findings in patients with late-onset multiple acyl-CoA dehydrogenase deficiency

Background:Late-onset multiple acyl-coA dehydrogenase deficiency (MADD) is an autosomal recessive inherited metabolic disorder. It is still unclear about the muscle magnetic resonance image (MRI) pattern of the distal lower limb pre- and post-treatment in patients with late-onset MADD. This study described the clinical and genetic findings in a cohort of patients with late-onset MADD, and aimed to characterize the MRI pattern of the lower limbs.Methods:Clinical data were retrospectively collected from clinic centers of Peking University People's Hospital between February 2014 and February 2018. Muscle biopsy, blood acylcarnitines, and urine organic acids profiles, and genetic analysis were conducted to establish the diagnosis of MADD in 25 patients. Muscle MRI of the thigh and leg were performed in all patients before treatment. Eight patients received MRI re-examinations after treatment.Results:All patients presented with muscle weakness or exercise intolerance associated with variants in the electron transfer flavoprotein dehydrogenase gene. Muscle MRI showed a sign of both edema-like change and fat infiltration selectively involving in the soleus (SO) but sparing of the gastrocnemius (GA) in the leg. Similar sign of selective involvement of the biceps femoris longus (BFL) but sparing of the semitendinosus (ST) was observed in the thigh. The sensitivity and specificity of the combination of either "SO+/GA-" sign or "BFL+/ST-" sign for the diagnosis of late-onset MADD were 80.0% and 83.5%, respectively. Logistic regression model supported the findings. The edema-like change in the SO and BFL muscles were quickly recovered at 1 month after treatment, and the clinical symptom was also relieved.Conclusions:This study expands the clinical and genetic spectrums of late-onset MADD. Muscle MRI shows a distinct pattern in the lower limb of patients with late-onset MADD. The dynamic change of edema-like change in the affected muscles might be a potential biomarker of treatment response.

Skeletal Muscle Magnetic Resonance Imaging of the Lower Limbs in Late-onset Lipid Storage Myopathy with Electron Transfer Flavoprotein Dehydrogenase Gene Mutations

Background： Lipid storage myopathy （LSM） is a genetically heterogeneous group with variable clinical phenotypes. Late-onset multiple acyl-coenzyme A dehydrogenation deficiency （MADD） is a rather common form of LSM in China. Diagnosis and clinical management of it remain challenging, especially without robust muscle biopsy result and genetic detection. As the noninvasion and convenience, muscle magnetic resonance imaging （MRI） is a helpful assistant, diagnostic tool for neuromuscular disorders. However, the disease-specific MRI patterns of muscle involved and its diagnostic value in late-onset MADD have not been systematic analyzed. Methods： We assessed the MRI pattern and fat infiltration degree of the lower limb muscles in 28 late-onset MADD patients, combined with detailed clinical features and gene spectrum. Fat infiltration degree of the thigh muscle was scored while that ofgluteus was described as obvious or not. Associated muscular atrophy was defined as obvious muscle bulk reduction. Results： The mean scores were significantly different among the anterior, medial, and posterior thigh muscle groups. The mean of fat infiltration scores on posterior thigh muscle group was significantly higher than either anterior or medial thigh muscle group （P 〈 0.00 l）. Moreover, the mean score on medial thigh muscle group was significantly higher than that of anterior thigh muscle group （P 〈 0.01）. About half of the patients displayed fat infiltration and atrophy in gluteus muscles. Of 28 patients, 12 exhibited atrophy in medial and/ or posterior thigh muscle groups, especially in posterior thigh muscle group. Muscle edema pattern was not found in all the patients. Conclusions： Late-onset MADD patients show a typical muscular imaging pattern of fat infiltration and atrophy on anterior, posterior, and medial thigh muscle groups, with major involvement of posterior thigh muscle group and gluteus muscles and a sparing involvement of anterior thigh compartment. Our findings also suggest that muscle MRI of lower limbs is a helpful tool in guiding clinical evaluation on late-onset MADD.

cDNA cloning, functional expression and cellular localization of rat liver mitochondrial electron-transfer flavoprotein-ubiquinone oxidoreductase protein

A membrane-bound protein was purified from rat liver mitochondria. After being di-gested with V8 protease, two peptides containing identical 14 amino acid residue sequences were obtained. Using the 14 amino acid peptide derived DNA sequence as gene specific primer, the cDNA of correspondent gene 5′-terminal and 3′-terminal were obtained by RACE technique. The full-length cDNA that encoded a protein of 616 amino acids was thus cloned, which included the above mentioned peptide sequence. The full length cDNA was highly homologous to that of human ETF-QO, indicating that it may be the cDNA of rat ETF-QO. ETF-QO is an iron sulfur protein located in mitochondria inner membrane containing two kinds of redox center: FAD and [4Fe-4S] center. After comparing the sequence from the cDNA of the 616 amino acids protein with that of the mature protein of rat liver mitochondria, it was found that the N terminal 32 amino acid residues did not exist in the mature protein, indicating that the cDNA was that of ETF-QOp. When the cDNA was expressed in Saccharomyces cerevisiae with inducible vectors, the protein product was enriched in mitochondrial fraction and exhibited electron transfer activity (NBT re-ductase activity) of ETF-QO. Results demonstrated that the 32 amino acid peptide was a mito-chondrial targeting peptide, and both FAD and iron-sulfur cluster were inserted properly into the expressed ETF-QO. ETF-QO had a high level expression in rat heart, liver and kidney. The fu-sion protein of GFP-ETF-QO co-localized with mitochondria in COS-7 cells.

Mechanistic Study of Oxidoreductase AprQ Involved in Biosynthesis of Aminoglycoside Antibiotic Apramycin

Main observation and conclusion The aminoglycoside antibiotic apramycin contains a unique bicyclic octose moiety,and biosynthesis of this moiety involves an oxidoreductase AprQ.Unlike other known“Q”series proteins involved in aminoglycosides biosynthesis,AprQ does not work with an aminotransferase partner,and performs a four-electron oxidation that converts a CH2OH moiety to a carboxylate group.