title: Assignment of a single disulfide bridge in rat liver methionine adenosyltransferase.
abstract: Rat liver methionine adenosyltransferase incorporated 8 mol of N-ethylmaleimide per mol of subunit upon denaturation in the presence of 8 M urea, whereas 10 such groups were labelled when dithiothreitol was also included. This observation prompted a re-examination of the state of the thiol groups, which was carried out using peptide mapping, amino acid analysis and N-terminal sequencing. The results obtained revealed a disulfide bridge between Cys35 and Cys61. This disulfide did not appear to be conserved because cysteines homologous to residue 61 do not exist in methionine adenosyltransferases of other origins, therefore suggesting its importance for the differential aspects of the liver-specific enzyme.
authors.affiliation: Instituto de Investigaciones Biomédicas 'Alberto Sols' (CSIC-UAM), Madrid, Spain.
authors.forename: M L
authors.initials: ML
authors.lastname: Martínez-Chantar
authors.forename: M A
authors.initials: MA
authors.lastname: Pajares
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002480:Cellulase / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism*; D004229:Dithiothreitol / Q000378:metabolism; D005033:Ethylmaleimide / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008716:Methionine Adenosyltransferase / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D020030:Nitric Oxide Donors / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010449:Peptide Mapping; D011489:Protein Denaturation / Q000187:drug effects; D020836:Protein Structure, Quaternary / Q000187:drug effects; D051381:Rats; D020539:Sequence Analysis, Protein; D014357:Trypsin / Q000378:metabolism; D014508:Urea / Q000494:pharmacology
chemical_list: D004220:Disulfides; D020030:Nitric Oxide Donors; D010446:Peptide Fragments; D014508:Urea; D008716:Methionine Adenosyltransferase; D002480:Cellulase; D014357:Trypsin; D003545:Cysteine; D005033:Ethylmaleimide; D004229:Dithiothreitol