Combination of NMR spectroscopy and X-ray crystallography offers unique advantages for elucidation of the structural basis of protein complex assembly

NMR spectroscopy and X-ray crystallography are two premium methods for determining the atomic structures of macro-biomolecular complexes.Each method has unique strengths and weaknesses.While the two techniques are highly complementary,they have generally been used separately to address the structure and functions of biomolecular complexes.In this review,we emphasize that the combination of NMR spectroscopy and X-ray crystallography offers unique power for elucidating the structures of complicated protein assemblies.We demonstrate,using several recent examples from our own laboratory,that the exquisite sensitivity of NMR spectroscopy in detecting the conformational properties of individual atoms in proteins and their complexes,without any prior knowledge of conformation,is highly valuable for obtaining the high quality crystals necessary for structure determination by X-ray crystallography.Thus NMR spectroscopy,in addition to answering many unique structural biology questions that can be addressed specifically by that technique,can be exceedingly powerful in modern structural biology when combined with other techniques including X-ray crystallography and cryo-electron microscopy.

2.2Ga Subduction-Related Mafic Magmatic Rocks in the Kongling Complex:Evidence for the Assembly of the Columbia Supercontinent

Objective Petrogenesis of the Paleoproterozoic mafic dikes and their tectonic implications are of great significance to the tectonic evolution of the Yangtze craton as well as the paleoposition of the Yangtze craton relative to the Columbia supercontinent.Till now,

Syntheses,Crystal Structures,DFT Calculation and Optical Properties of a Schiff Base and Its Dinuclear Mercury(Ⅱ)Complex

A pyridine-contained Schiff base ligand L（L =（pyridine-2-vinyl）hydrazine） has been synthesized and fully characterized. By self-assembly of the ligand with HgI2, a binuclear complex Hg2I4L（C） was obtained. The structures of L and C were analyzed through single-crystal X-ray diffraction. L crystallizes in monoclinic, space group P21/n with a=11.286（5）, b=3.981（5）, c=23.865（5） , β=100.043（5）°, V=1056（1） 3, Z=4, Dc=1.323 g/m3, F（000）=440, Μr=210.24, μ=0.084 mm（-1）, the final R=0.0928 and w R=0.2867 for 6955 observed reflections with I ＆gt; 2（I）. The complex is of monoclinic system, space group P21/n with a=8.706（5）, b=17.468（5）, c=14.675（5） , β=93.922（5）°, V=2227（2） 3, Z=4, Dc=3.338 g/m3, F（000）=1928, Μr=1119.02, μ=19.321 mm（-1）, the final R=0.0366 and w R=0.1276 for 3920 observed reflections with I ＆gt; 2（I）. The structural analysis revealed that the molecule of L possesses a well planar structure. However, in the complex, the coordinated ligand distorts greatly. The absorption spectra of L and the complex in ethanol were experimentally and theoretically studied. The result indicates that the complex exhibits different absorption spectrum compared with the free ligand.

Alb4 of Arabidopsis Promotes Assembly and Stabilization of a Non Chlorophyll-Binding Photosynthetic Complex, the CF1CF0-ATP Synthase

All members of the YidC/Oxal/Alb3 protein family are evolutionarily conserved and appear to function in membrane protein integration and protein complex stabilization. Here, we report on a second thylakoidal isoform of Alb3, named Alb4. Analysis of Arabidopsis knockout mutant lines shows that AIb4 is required in assembly and/or stability of the CF1CF0-ATP synthase （ATPase）. alb4 mutant lines not only have reduced steady-state levels of ATPase subunits, but also their assembly into high-molecular-mass complexes is altered, leading to a reduction of ATP synthesis in the mutants. Moreover, we show that Alb4 but not AIb3 physically interacts with the subunits CF1β and CF0ll. Summarizing, the data indicate that AIb4 functions to stabilize or promote assembly of CF1 during its attachment to the membrane-embedded CF0 part.

SUMOylation facilitates the assembly of a Nuclear Factor-Y complex to enhance thermotolerance in Arabidopsis

Heat stress(HS) has serious negative effects on plant development and has become a major threat to agriculture. A rapid transcriptional regulatory cascade has evolved in plants in response to HS. Nuclear Factor-Y(NF-Y) complexes are critical for this mechanism, but how NF-Y complexes are regulated remains unclear.In this study, we identified NF-YC10(NF-Y subunit C10), a central regulator of the HS response in Arabidopsis thaliana, as a substrate of SUMOylation, an important post-translational modification. Biochemical analysis showed that the SUMO ligase SIZ1(SAP AND MIZ1 DOMAINCONTAINING LIGASE1) interacts with NF-YC10and enhances its SUMOylation during HS. The SUMOylation of NF-YC10 facilitates its interaction with and the nuclear translocation of NF-YB3, in which the SUMO interaction motif(SIM)is essential for its efficient association with NF-YC10. Further functional analysis indicated that the SUMOylation of NF-YC10 and the SIM of NF-YB3 are critical for HS-responsive gene expression and plant thermotolerance. These findings uncover a role for the SIZ1-mediated SUMOylation of NF-YC10 in NF-Y complex assembly under HS, providing new insights into the role of a post-translational modification in regulating transcription during abiotic stress responses in plants.

Synthesis and Structure of a Ladder-like Co-crystal Cu^ICl with 3,5-Dipropyl-4-amino-1,2,4-triazole

Redox reaction of a mixture of CuC12·2H2O, HaPO3 and dpatrz （3,5-dipropyl- 4-amino-1,2,4-triazole） at room temperature yields one new compound, [Cu（1）（/.t2-dpatrz）aCu（1）CI2], with two independent cis- and trans-propyl side chain molecules. Compound 1 crystallizes in monoclinic, space group P21/c with a = 7.474（1）, b = 17.807（1）, c = 18.851（1） A, β = 108.32（1）°, V = 2381.7（2） A3, Z = 4, C16H32CI2Cu2Ns, Mr = 534.48, Dc = 1.491 g.cm-3,μ = 2.03 mm-1, F（000） = 1104, GOOF = 1.050, the final R = 0.0445 and wR = 0.1162 for 3162 observed reflections （I 〉 2σ（I））. Compound 1 shows discrete dimeric structures （A and B） containing inversion centers and the Cu（l） ions are coordinated in triangle geometries. The isomers are connected by N-H…CI hydrogen bonds, chains with graph-set C（7） and rings R22（14） and C-H..＇Jr interactions into stair-step chains （Tapes A and B） running parallel to the [01-1] direction. The N-H…C1 hydrogen bonds result in chain and cyclic structures with graph-sets C22（17） and R34（18） linking tapes A and B to form two-dimensional networks along the [031] direction. Packing of crystal 1 is stabilized by rings R34（18） and weak C-H…C1 hydrogen bonds parallel to the [01-2] direction. Bond valence sum （BVS） and UV-Vis absorption spectra support the existence of Cu（I） ions. Compound 1 exhibits extensive green blue phosphorescence in the solid state at room temperature.

Synthesis and luminescent properties of a silylated-terpyridine derivative and its metalated complexes in solutions and self-assembled monolayers

A silylated-terpyridine（Si TPy） derivative was newly synthesized and reacted with various transition metal ions in the solutions and self-assembled monolayers（SAMs）.Composition and morphology of the SAMs were characterized by using absorption spectra,X-ray photoelectron spectra and atomic force microscope.The silylated-TPy compound gave off a luminescent emission at about 456 nm,which slightly shifted to 452 nm in the Zn^2＋-Si TPy and Fe^2＋-Si TPy metalated complexes.The absorbed energy can be further transferred to lanthanide ions（Tb^3＋and Eu^3＋） to give off the typical emissions of the lanthanide complexes together with an emission of the silylated-TPy at about 363 nm.

Interfacial assembly and host-guest interaction of anthracene-conjugated L-glutamate dendron with cyclodextrin at the air/water interface

The interracial assembly of photo-induced dimerization of atypical anthracene-containing amphiphilic dendron and host-guest interaction with γ-cyclodextrin has been investigated. It has been proved that even without long alkyl chain the amphiphilic dendron could still form stable Langmuir monolayer at the air/water interface. Through the host-guest interaction,γ-cyclodextrin can be used to encapsulate two headgroups of amphiphilic dendron in the antiparallel direction. However, the formed host-guest complex was sensitive to the surface pressure. Slight compression of surface pressure led amphiphilic dendron to reassemble into nanofibers through the strong π-π stacking between headgroups. On the other hand, under in situ irradiation, the amphiphilic dendron was stabilized in the cavity of γ- cyclodextrin through headgroup dimerization and the host-guest complex further irregularly aggregated to nanoparticles. Meanwhile, γ-cyclodextrin, as a silencer, blocked the supramolecular chirality transfer. Our conclusion was demonstrated through UV/vis, FT-IR, CD spectrum and AFM images, respectively.

Mitochondrial Composition,Function and Stress Response in Plants

The primary function of mitochondria is respiration, where catabolism of substrates is coupled to ATP synthesis via oxidative phosphorylation. In plants, mitochondrial composition is relatively complex and flexible and has specific pathways to support photosynthetic processes in illuminated leaves.

Nucleus-Encoded Light-Harvesting Chlorophyll a/b Proteins are Imported Normally into Chlorophyll b-Free Chloroplasts of Arabidopsis

Chloroplast-located proteins which are encoded by the nuclear genome have to be imported from the cytosol into the organelle in a posttranslational manner. Among these nuclear-encoded chloroplast proteins are the light- harvesting chlorophyll a/b-binding proteins （LHCPs）. After translation in the cytosol, precursor proteins of LHCPs are imported via the TOC/TIC translocase, processed to their mature size to insert into thylakoid membranes where they recruit chlorophylls a and b to form pigment-protein complexes. The translocation of proteins is a highly regulated process which employs several regulators. To analyze whether CAO （chlorophyll a oxigenase） which converts chlorophyll a to chlorophyll b at the inner chloroplast membrane, is one of these regulators, we performed import reactions utilizing a homozygous loss-of-function mutant （cao-1）. We imported in vitro translated and 35S-labeled precursor proteins of light- harvesting proteins of photosystem II LHCB1, LHCB4, and LHCB5 into chloroplasts isolated from cao-1 and show that import of precursor proteins and their processing to mature forms are not impaired in the mutant. Therefore, regulation of the import machinery cannot be responsible for the decreased steady-state levels of light-harvesting complex （LHC） proteins. Regulation does not take place at the transcriptional level either, because Lhcb mRNAs are not down-regulated. Additionally, reduced steady-state levels of LHCPs also do not occur due to posttranslational turnover of non-functional LHCPs in chloroplasts. Taken together, our data show that plants in the absence of CAO and therefore devoid of chlorophyll b are not influenced in their import behavior of LHC proteins.

REEP1 Preserves Motor Function in SOD1^(G93A) Mice by Improving Mitochondrial Function via Interaction with NDUFA4

A decline in the activities of oxidative phosphorylation(OXPHOS)complexes has been consistently reported in amyotrophic lateral sclerosis(ALS)patients and animal models of ALS,although the underlying molecular mechanisms are still elusive.Here,we report that receptor expression enhancing protein 1(REEP1)acts as an important regulator of complex IV assembly,which is pivotal to preserving motor neurons in SOD1^(G93A) mice.We found the expression of REEP1 was greatly reduced in transgenic SOD1^(G93A) mice with ALS.Moreover,forced expression of REEP1 in the spinal cord extended the lifespan,decelerated symptom progression,and improved the motor performance of SOD1^(G93A) mice.The neuromuscular synaptic loss,gliosis,and even motor neuron loss in SOD1^(G93A) mice were alleviated by increased REEP1 through augmentation of mitochondrial function.Mechanistically,REEP1 associates with NDUFA4,and plays an important role in preserving the integrity of mitochondrial complex IV.Our findings offer insights into the pathogenic mechanism of REEP1 deficiency in neurodegenerative diseases and suggest a new therapeutic target for ALS.