Open AccessAssignment of a single disulfide bridge in rat liver methionine adenosyltransferase
Author(s) -
MartínezChantar María L.,
Pajares María A.
Publication year - 2000
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2000.00974.x
Subject(s) - dithiothreitol , methionine adenosyltransferase , methionine , disulfide bond , chemistry , biochemistry , protein subunit , cysteine , enzyme , thiol , cystine , peptide , amino acid , urea , residue (chemistry) , stereochemistry , gene
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.