title: Existence of molten globule state in homocysteine-induced protein covalent modifications.
abstract: Homocysteine thiolactone is a toxic metabolite produced from homocysteine by amino-acyl t-RNA synthetase in error editing reaction. The basic cause of toxicity of homocysteine thiolactone is believed to be due to the adduct formation with lysine residues (known as protein N-homocysteinylation) leading to protein aggregation and loss of enzyme function. There was no data available until now that showed the effect of homocysteine thiolactone on the native state structural changes that led to aggregate formation. In the present study we have investigated the time dependent structural changes due to homocysteine thiolactone induced modifications on three different proteins having different physico-chemical properties (cytochrome-c, lysozyme and alpha lactalbumin). We discovered that N-homocysteinylation leads to the formation of molten globule state--an important protein folding intermediate in the protein folding pathway. We also found that the formation of the molten globule state might be responsible for the appearance of aggregate formation. The study indicates the importance of protein folding intermediate state in eliciting the homocysteine thiolactone toxicity.
authors.affiliation: Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi, India.
authors.forename: Tarun
authors.initials: T
authors.lastname: Kumar
authors.affiliation: Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi, India.
authors.forename: Gurumayum Suraj
authors.initials: GS
authors.lastname: Sharma
authors.affiliation: Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi, India.
authors.forename: Laishram Rajendrakumar
authors.initials: LR
authors.lastname: Singh
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002645:Chickens; D002942:Circular Dichroism; D045304:Cytochromes c / Q000737:chemistry; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000737:chemistry; D007768:Lactalbumin / Q000737:chemistry; D009113:Muramidase / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D011506:Proteins; D006710:Homocysteine; D045304:Cytochromes c; D007768:Lactalbumin; C007957:homocysteine thiolactone; D009113:Muramidase