The binding of small diatomic ligands such as carbon monoxide or dioxygen to heme proteins is among the simplest biological processes known. Still, it has taken many decades to understand the mechanistic aspects of th...The binding of small diatomic ligands such as carbon monoxide or dioxygen to heme proteins is among the simplest biological processes known. Still, it has taken many decades to understand the mechanistic aspects of this process in full detail. Here, we compare ligand binding in three heme proteins of the globin family, myoglobin, a dimeric hemoglobin, and neuroglobin. The combination of structural, spectroscopic, and kinetic experiments over many years by many laboratories has revealed common properties of globins and a clear mechanistic picture of ligand binding at the molecular level. In addition to the ligand binding site at the heme iron, a primary ligand docking site exists that ensures efficient ligand binding to and release from the heme iron. Additional, secondary docking sites can greatly facilitate ligand escape after its dissociation from the heme. Although there is only indirect evidence at present, a preformed histidine gate appears to exist that allows ligand entry to and exit from the active site. The importance of these features can be assessed by studies involving modified proteins（via site-directed mutagenesis） and comparison with heme proteins not belonging to the globin family.展开更多
Potential toxicity of transition metals like Hg, Cu and Cd are well known and their affinity toward proteins is of great concern. This work explores the selective nature of interactions of Cu2＋, Hg2＋ and Cd2＋ with ...Potential toxicity of transition metals like Hg, Cu and Cd are well known and their affinity toward proteins is of great concern. This work explores the selective nature of interactions of Cu2＋, Hg2＋ and Cd2＋ with the heme proteins leghemoglobin, myoglobin and cytochrome C. The binding profiles were analyzed using absorbance spectrum and steady-state fluorescence spectroscopy. Thermodynamic parameters like enthalpy, entropy and free energy changes were derived by isothermal calorimetry and consequent binding parameters were compared for these heme proteins. Free energy （AG） values revealed Cu2＋ binding toward myoglobin and leghemoglobin to be specific and facile in contrast to weak binding for Hg2＋ or Cd2＋ . Time correlated single photon counting indicated significant alteration in excited state lifetimes for metal complexed myoglobin and leghemoglobin suggesting bimolecular collisions to be involved. Interestingly, none of these cations showed significant affinity for cytochrome c pointing that, presence of conserved sequences or heme group is not the only criteria for cation binding toward heme proteins, but the microenvironment of the residues or a specific folding pattern may be responsible for these differential conjugation profile. Binding of these cations may modulate the conformation and functions of these biologically important proteins.展开更多
Heme proteins play various important roles in a variety of physiological and pathological processes.Surfactant assemblies have drawn great attention in fabricating fluorescent sensors to detect and identify proteins.I...Heme proteins play various important roles in a variety of physiological and pathological processes.Surfactant assemblies have drawn great attention in fabricating fluorescent sensors to detect and identify proteins.In this study,an acetylpyrene fluorophore containing imidazole HP-1 was synthesized,and it could be well modulated by an anionic surfactant sodium dodecyl sulfate(SDS).The selected ensemble based on HP-1/SDS assemblies exhibited selective fluorescence sensing performance towards the heme proteins,including neuroglobin(Ngb),myoglobin(Mb)and cytochrome c(Cyt c).Besides,phospholipid DMPC vesicles as membrane models were particularly explored the association process between the heme protein Mb and membrane.The present work showed that Mb induced the lysis of DMPC liposomes visualized by transmission electron microscopy and optical microscope.展开更多
BACKGROUND Enterotoxigenic Bacteroides fragilis(ETBF)causes colitis and diarrhea,and is considered a candidate pathogen in inflammatory bowel diseases as well as colorectal cancers.These diseases are dependent on ETBF...BACKGROUND Enterotoxigenic Bacteroides fragilis(ETBF)causes colitis and diarrhea,and is considered a candidate pathogen in inflammatory bowel diseases as well as colorectal cancers.These diseases are dependent on ETBF-secreted toxin(BFT).Dendritic cells(DCs)play an important role in directing the nature of adaptive immune responses to bacterial infection and heme oxygenase-1(HO-1)is involved in the regulation of DC function.AIM To investigate the role of BFT in HO-1 expression in DCs.METHODS Murine DCs were generated from specific pathogen-free C57BL/6 and Nrf2−/−knockout mice.DCs were exposed to BFT,after which HO-1 expression and the related signaling factor activation were measured by quantitative RT-PCR,EMSA,fluorescent microscopy,immunoblot,and ELISA.RESULTS HO-1 expression was upregulated in DCs stimulated with BFT.Although BFT activated transcription factors such as NF-κB,AP-1,and Nrf2,activation of NF-κB and AP-1 was not involved in the induction of HO-1 expression in BFT-exposed DCs.Instead,upregulation of HO-1 expression was dependent on Nrf2 activation in DCs.Moreover,HO-1 expression via Nrf2 in DCs was regulated by mitogenactivated protein kinases such as ERK and p38.Furthermore,BFT enhanced the production of reactive oxygen species(ROS)and inhibition of ROS production resulted in a significant decrease of phospho-ERK,phospho-p38,Nrf2,and HO-1 CONCLUSION These results suggest that signaling pathways involving ROS-mediated ERK and p38 mitogen-activated protein kinases-Nrf2 activation in DCs are required for HO-1 induction during exposure to ETBF-produced BFT.展开更多
AIM:To assess effects of heme on messenger RNA(mRNA) and microRNA(miRNA) profiles of liver cells derived from humans.METHODS:We exposed human hepatoma cell line Huh-7 cells to excess iron protoporphyrin(heme)(10 μmol...AIM:To assess effects of heme on messenger RNA(mRNA) and microRNA(miRNA) profiles of liver cells derived from humans.METHODS:We exposed human hepatoma cell line Huh-7 cells to excess iron protoporphyrin(heme)(10 μmol/L) or induced heme deficiency by addition of 4,6-dioxoheptanoic acid(500 μmol/L),a potent inhibitor of aminolevulinic acid dehydratase,for 6 h or 24 h.We harvested total RNA from the cells and performed both mRNA and miRNA array analyses,with use of Affymetrix chips,reagents,and instruments(human genome U133 plus 2.0 and miRNA 2.0 arrays).We assessed changes and their significance and interrelationships with Target Scan,Pathway Studios,and Ingenuity software.RESULTS:Changes in mRNA levels were most numerous and striking at 6 h after heme treatment but were similar and still numerous at 24 h.After 6 h of heme exposure,the increase in heme oxygenase 1 gene expression was 60-fold by mRNA and 88-fold by quantitative reverse transcription-polymerase chain reaction.We found striking changes,especially up-regulation by heme of nuclear erythroid-2 related factor-mediated oxidative stress responses,protein ubiquitination,glucocorticoid signaling,P53 signaling,and changes in RNAs that regulate intermediary metabolism.Fewer mRNAs were down-regulated by heme,and the fold decreases were less exuberant than were the increases.Notable decreases after 24 h of heme exposure were patatin-like phospholipase domain-containing protein 3(-6.5-fold),neuronal PAS domain protein 2(-1.93-fold),and protoporphyrinogen oxidase(-1.7-fold).CONCLUSION:Heme excess exhibits several toxic effects on liver and kidney,which deserve study in humans and in animal models of the human porphyrias or other disorders.展开更多
Benfang Lei's laboratory conducts research on pathogenesis of human pathogen Group A Streptococcus (GAS)and horse pathogen Streptococcus equi(S.equi). His current research focuses on heme acquisition in Gram-posit...Benfang Lei's laboratory conducts research on pathogenesis of human pathogen Group A Streptococcus (GAS)and horse pathogen Streptococcus equi(S.equi). His current research focuses on heme acquisition in Gram-positive pathogens and molecular mechanism of GAS and S.equi pathogenesis.Heme is an important source of essential iron for bacterial pathogens.Benfang Lei and colleagues identified the first cell surface heme-binding protein in Gram-positive pathogens and the heme acquisition system in GAS,demonstrated direct heme transfer from one protein to another,demonstrated an experimental pathway of heme acquisition by the Staphylococcus aureus Isd system,elucidated the activated heme transfer mechanism,and obtained evidence for a chemical mechanism of direct axial ligand displacement during the Shp-to-HtsA heme transfer reaction.These findings have considerably contributed to the progress that has been made over recent years in understanding the heme acquisition process in Grampositive pathogens.Pathogenesis of GAS is mediated by an abundance of extracellular proteins,and pathogenic role and functional mechanism are not known for many of these virulence factors.Lei laboratory identified a secreted protein of GAS as a CovRS-regulated virulence factor that is a protective antigen and is critical for GAS spreading in the skin and systemic dissemination.These studies may lead to development of novel strategies to prevent and treat GAS infections.展开更多
基金supported by the Deutsche Forschungsgemeinschaft (DFG, grant Ni291/10)
文摘The binding of small diatomic ligands such as carbon monoxide or dioxygen to heme proteins is among the simplest biological processes known. Still, it has taken many decades to understand the mechanistic aspects of this process in full detail. Here, we compare ligand binding in three heme proteins of the globin family, myoglobin, a dimeric hemoglobin, and neuroglobin. The combination of structural, spectroscopic, and kinetic experiments over many years by many laboratories has revealed common properties of globins and a clear mechanistic picture of ligand binding at the molecular level. In addition to the ligand binding site at the heme iron, a primary ligand docking site exists that ensures efficient ligand binding to and release from the heme iron. Additional, secondary docking sites can greatly facilitate ligand escape after its dissociation from the heme. Although there is only indirect evidence at present, a preformed histidine gate appears to exist that allows ligand entry to and exit from the active site. The importance of these features can be assessed by studies involving modified proteins（via site-directed mutagenesis） and comparison with heme proteins not belonging to the globin family.
文摘Potential toxicity of transition metals like Hg, Cu and Cd are well known and their affinity toward proteins is of great concern. This work explores the selective nature of interactions of Cu2＋, Hg2＋ and Cd2＋ with the heme proteins leghemoglobin, myoglobin and cytochrome C. The binding profiles were analyzed using absorbance spectrum and steady-state fluorescence spectroscopy. Thermodynamic parameters like enthalpy, entropy and free energy changes were derived by isothermal calorimetry and consequent binding parameters were compared for these heme proteins. Free energy （AG） values revealed Cu2＋ binding toward myoglobin and leghemoglobin to be specific and facile in contrast to weak binding for Hg2＋ or Cd2＋ . Time correlated single photon counting indicated significant alteration in excited state lifetimes for metal complexed myoglobin and leghemoglobin suggesting bimolecular collisions to be involved. Interestingly, none of these cations showed significant affinity for cytochrome c pointing that, presence of conserved sequences or heme group is not the only criteria for cation binding toward heme proteins, but the microenvironment of the residues or a specific folding pattern may be responsible for these differential conjugation profile. Binding of these cations may modulate the conformation and functions of these biologically important proteins.
基金financially supported by the Scientific Research Fund of Hunan Education Department,China(Nos.21B0421,20C1636)The National Natural Science Foundation of China(No.21977042)。
文摘Heme proteins play various important roles in a variety of physiological and pathological processes.Surfactant assemblies have drawn great attention in fabricating fluorescent sensors to detect and identify proteins.In this study,an acetylpyrene fluorophore containing imidazole HP-1 was synthesized,and it could be well modulated by an anionic surfactant sodium dodecyl sulfate(SDS).The selected ensemble based on HP-1/SDS assemblies exhibited selective fluorescence sensing performance towards the heme proteins,including neuroglobin(Ngb),myoglobin(Mb)and cytochrome c(Cyt c).Besides,phospholipid DMPC vesicles as membrane models were particularly explored the association process between the heme protein Mb and membrane.The present work showed that Mb induced the lysis of DMPC liposomes visualized by transmission electron microscopy and optical microscope.
基金Supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology,South Korea,No.NRF-2018R1D1A1B07043350
文摘BACKGROUND Enterotoxigenic Bacteroides fragilis(ETBF)causes colitis and diarrhea,and is considered a candidate pathogen in inflammatory bowel diseases as well as colorectal cancers.These diseases are dependent on ETBF-secreted toxin(BFT).Dendritic cells(DCs)play an important role in directing the nature of adaptive immune responses to bacterial infection and heme oxygenase-1(HO-1)is involved in the regulation of DC function.AIM To investigate the role of BFT in HO-1 expression in DCs.METHODS Murine DCs were generated from specific pathogen-free C57BL/6 and Nrf2−/−knockout mice.DCs were exposed to BFT,after which HO-1 expression and the related signaling factor activation were measured by quantitative RT-PCR,EMSA,fluorescent microscopy,immunoblot,and ELISA.RESULTS HO-1 expression was upregulated in DCs stimulated with BFT.Although BFT activated transcription factors such as NF-κB,AP-1,and Nrf2,activation of NF-κB and AP-1 was not involved in the induction of HO-1 expression in BFT-exposed DCs.Instead,upregulation of HO-1 expression was dependent on Nrf2 activation in DCs.Moreover,HO-1 expression via Nrf2 in DCs was regulated by mitogenactivated protein kinases such as ERK and p38.Furthermore,BFT enhanced the production of reactive oxygen species(ROS)and inhibition of ROS production resulted in a significant decrease of phospho-ERK,phospho-p38,Nrf2,and HO-1 CONCLUSION These results suggest that signaling pathways involving ROS-mediated ERK and p38 mitogen-activated protein kinases-Nrf2 activation in DCs are required for HO-1 induction during exposure to ETBF-produced BFT.
基金Supported by A Grant from NIH/NIDDK (DK38825) to Bonkovsky HLInstitutional Funds from the Carolinas Health Care Foundation and Carolinas Medical Center
文摘AIM:To assess effects of heme on messenger RNA(mRNA) and microRNA(miRNA) profiles of liver cells derived from humans.METHODS:We exposed human hepatoma cell line Huh-7 cells to excess iron protoporphyrin(heme)(10 μmol/L) or induced heme deficiency by addition of 4,6-dioxoheptanoic acid(500 μmol/L),a potent inhibitor of aminolevulinic acid dehydratase,for 6 h or 24 h.We harvested total RNA from the cells and performed both mRNA and miRNA array analyses,with use of Affymetrix chips,reagents,and instruments(human genome U133 plus 2.0 and miRNA 2.0 arrays).We assessed changes and their significance and interrelationships with Target Scan,Pathway Studios,and Ingenuity software.RESULTS:Changes in mRNA levels were most numerous and striking at 6 h after heme treatment but were similar and still numerous at 24 h.After 6 h of heme exposure,the increase in heme oxygenase 1 gene expression was 60-fold by mRNA and 88-fold by quantitative reverse transcription-polymerase chain reaction.We found striking changes,especially up-regulation by heme of nuclear erythroid-2 related factor-mediated oxidative stress responses,protein ubiquitination,glucocorticoid signaling,P53 signaling,and changes in RNAs that regulate intermediary metabolism.Fewer mRNAs were down-regulated by heme,and the fold decreases were less exuberant than were the increases.Notable decreases after 24 h of heme exposure were patatin-like phospholipase domain-containing protein 3(-6.5-fold),neuronal PAS domain protein 2(-1.93-fold),and protoporphyrinogen oxidase(-1.7-fold).CONCLUSION:Heme excess exhibits several toxic effects on liver and kidney,which deserve study in humans and in animal models of the human porphyrias or other disorders.
基金Supported by National Institutes of Health Grants AI057347 and P20 RR-020185US Department of Agriculture National Research Initiative/Competitive Grants Program Grants 2006-01690 and 2007-35204-18306+2 种基金Montana Board of Research and Commercialization Technology Grant#07-51USDA Animal Health Formula Fundsthe Montana State Agricultural Experiment Station
文摘Benfang Lei's laboratory conducts research on pathogenesis of human pathogen Group A Streptococcus (GAS)and horse pathogen Streptococcus equi(S.equi). His current research focuses on heme acquisition in Gram-positive pathogens and molecular mechanism of GAS and S.equi pathogenesis.Heme is an important source of essential iron for bacterial pathogens.Benfang Lei and colleagues identified the first cell surface heme-binding protein in Gram-positive pathogens and the heme acquisition system in GAS,demonstrated direct heme transfer from one protein to another,demonstrated an experimental pathway of heme acquisition by the Staphylococcus aureus Isd system,elucidated the activated heme transfer mechanism,and obtained evidence for a chemical mechanism of direct axial ligand displacement during the Shp-to-HtsA heme transfer reaction.These findings have considerably contributed to the progress that has been made over recent years in understanding the heme acquisition process in Grampositive pathogens.Pathogenesis of GAS is mediated by an abundance of extracellular proteins,and pathogenic role and functional mechanism are not known for many of these virulence factors.Lei laboratory identified a secreted protein of GAS as a CovRS-regulated virulence factor that is a protective antigen and is critical for GAS spreading in the skin and systemic dissemination.These studies may lead to development of novel strategies to prevent and treat GAS infections.
