Conformational and ligand binding properties of the isolated domains from the beta 2 subunit of Escherichia coli tryptophan synthetase investigated by the reactivity of their cysteines.

摘要: A mild proteolytic treatment of the dimeric beta 2 subunit Escherichia coli tryptophan synthetase (L-serine hydrolase (adding indole) EC 4.2.1.20) is known to nick each polypeptide chain into two complementary fragments, F1 and F2 (Hogberg-Railbaud, A., Goldberg, M.E. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 442-446). The reactivity cysteines in isolated or associated fragments studied used characterize structural functional properties these fragments. It shown that total number cysteines, their dithiobisnitrobenzoate, protection by various ligands are same nicked intact enzyme, thus demonstrating close analogy between proteins. In reactive buried, confirming this has a compact, globular structure. Various tested fail produce any modification suggesting none alone carries binding site for substrates coenzyme.