2v03
From Proteopedia
High resolution structure and catalysis of an O-acetylserine sulfhydrylase
Structural highlights
FunctionCYSM_ECOLI Two cysteine synthase enzymes are found. Both catalyze the same reaction. Cysteine synthase B can also use thiosulfate in place of sulfide to give cysteine thiosulfonate as a product. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe crystal structure of the dimeric O-acetylserine sulfhydrylase isozyme B from Escherichia coli (CysM), complexed with the substrate analog citrate, has been determined at 1.33 A resolution by X-ray diffraction analysis. The C1-carboxylate of citrate was bound at the carboxylate position of O-acetylserine, whereas the C6-carboxylate adopted two conformations. The activity of the enzyme and of several active center mutants was determined using an assay based on O-acetylserine and thio-nitrobenzoate (TNB). The unnatural substrate TNB was modeled into the reported structure. The substrate model and the observed mutant activities may facilitate future protein engineering attempts designed to broaden the substrate spectrum of the enzyme. A comparison of the reported structure with previously published CysM structures revealed large conformational changes. One of the crystal forms contained two dimers, each of which comprised one subunit in a closed and one in an open conformation. Although the homodimer asymmetry was most probably caused by crystal packing, it indicates that the enzyme can adopt such a state in solution, which may be relevant for the catalytic reaction. High resolution structure and catalysis of O-acetylserine sulfhydrylase isozyme B from Escherichia coli.,Zocher G, Wiesand U, Schulz GE FEBS J. 2007 Oct;274(20):5382-9. Epub 2007 Sep 26. PMID:17894825[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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