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Cysteine‐25 of adenylate kinase reacts with dithiothreitol to form an adduct upon aging of the enzyme
Author(s) -
Li Xia,
Han Yang,
Pan Xian Ming
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02954-4
Subject(s) - dithiothreitol , chemistry , cysteine , adduct , adenylate kinase , enzyme , guanidine , guanidinium chloride , hydrochloride , stereochemistry , biochemistry , medicinal chemistry , organic chemistry
Adenylate kinase (AK) ages in solution in the presence of DL ‐dithiothreitol (DTT) with a gradual activity decrease. Upon dilution with 4 M guanidine hydrochloride denatured native and aged AK, both recover to the same activity as the fresh enzyme. Mass spectroscopy and 7‐chloro‐4‐nitrobenz‐2‐oxa‐1,3‐diazole chloride modification kinetics studies identify that the residue cysteine‐25 of the enzyme reacts with DTT to form an adduct. The formation of the unusual bridging DTT adduct of AK appears to be the result of a stable DTT–protein complex. The K M for AMP, ADP and MgATP of the DTT‐modified enzyme does not differ significantly from that of the intact enzyme, whereas the secondary and tertiary structures of the enzyme change obviously. These results indicate that cysteine‐25 may not be involved directly in substrate binding, but may play an important role in maintaining secondary and tertiary structures of native AK, as well as the conformation interconversion in the catalytic cycle.