Abstract
Leishmania major 3-mercaptopyruvate sulfurtransferase is a crescent-shaped molecule comprising three domains. The N-terminal and central domains are similar to the thiosulfate sulfurtransferase rhodanese and create the active site containing a persulfurated catalytic cysteine (Cys-253) and an inhibitory sulfite coordinated by Arg-74 and Arg-185. A serine protease-like triad, comprising Asp-61, His-75, and Ser-255, is near Cys-253 and represents a conserved feature that distinguishes 3-mercaptopyruvate sulfurtransferases from thiosulfate sulfurtransferases. During catalysis, Ser-255 may polarize the carbonyl group of 3-mercaptopyruvate to assist thiophilic attack, whereas Arg-74 and Arg-185 bind the carboxylate group. The enzyme hydrolyzes benzoyl-Arg-p-nitroanilide, an activity that is sensitive to the presence of the serine protease inhibitor N alpha-p-tosyl-L-lysine chloromethyl ketone, which also lowers 3-mercaptopyruvate sulfurtransferase activity, presumably by interference with the contribution of Ser-255. The L. major 3-mercaptopyruvate sulfurtransferase is unusual with an 80-amino acid C-terminal domain, bearing remarkable structural similarity to the FK506-binding protein class of peptidylprolyl cis/trans-isomerase. This domain may be involved in mediating protein folding and sulfurtransferase-protein interactions.
Highlights
Leishmania major 3-mercaptopyruvate sulfurtransferase is a crescent-shaped molecule comprising three domains
The active site, with a catalytic cysteine, is situated in a cleft formed at the interface of the domains, it is mainly constructed from residues associated with the C-terminal domain
It has been shown that mercaptopyruvate:cyanide sulfurtransferase (MST) contain a serine protease-like catalytic triad in their active site
Summary
Leishmania major 3-mercaptopyruvate sulfurtransferase is a crescent-shaped molecule comprising three domains. The L. major 3-mercaptopyruvate sulfurtransferase is unusual with an 80-amino acid C-terminal domain, bearing remarkable structural similarity to the FK506-binding protein class of peptidylprolyl cis/trans-isomerase. This domain may be involved in mediating protein folding and sulfurtransferase-protein interactions. Sulfurtransferases (EC 2.8.1.1–5) catalyze the transfer of sulfane sulfur from a donor molecule to a thiophilic acceptor These enzymes are widely distributed in plants, animals, and bacteria [1,2,3] and have been implicated in a wide range of biological processes. The active site, with a catalytic cysteine, is situated in a cleft formed at the interface of the domains, it is mainly constructed from residues associated with the C-terminal domain. This domain is often termed the active domain, whereas the Nterminal domain is described as inactive
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