ANALYSIS BY LIMITED PROTEOLYSIS OF DOMAIN ORGANIZATION AND GSH-SITE ARRANGEMENT OF BACTERIAL GLUTATHIONE TRANSFERASE B1-1

Limited proteolysis method has been used to study the structure-function relationship of bacterial glutathione transferase (GSTB1-1). In absence of three-dimensional structural data of prokaryote GST, the results represent the first information concerning the G-site and domains organization of GSTB1-1. The tryptic cleavages occur mainly at the peptide bonds Lys35-Lys36 and Phe43-Leu44, generating two major molecular species of 20-kDa, 3-kDa and traces of 10-kDa. 1-chloro-2,4-dinitrobenzene favoured the proteolysis of the 20-kDa fragment markedly enhancing the production of the 10-kDa peptide by cleaving the chemical bonds Lys87-Ala88 and Arg91-Tyr92. The tryptic cleavage sites of GSTB1-1 was found to be located close to those previously found for the mammalian GSTP1-1 isozyme. It was concluded that despite their low sequence homology (18%), GSTB1-1 and GSTP1-1 displayed similar structural features in their G-site regions and probably a common organization in structural domains.