Structural highlights
FunctionVIBB_VIBCH Involved in the biosynthesis of the catechol siderophore vibriobactin. Vibriobactin is a chelating compound involved in transporting iron from the bacterial environment into the cell cytoplasm. Publication Abstract from PubMedThe N-terminal isochorismatase (ISC) domain of VibB (VibB-ISC) catalyzes the vinyl ether hydrolysis of isochorismate to 2,3-dihydro-2,3-dihydroxybenzoate and pyruvate. Structures of the ISC domain and its complex with isochorismate have been determined at 1.35 and 1.10 A resolution, respectively. Two catalytic waters which were absent from previously reported homologous structures were observed adjacent to isochorismate and the catalytic residues (Asp35 and Lys118) in the VibB-ISC complex. Molecular-dynamics (MD) simulations starting with the structure of the VibB-ISC complex suggest that the catalytic waters contribute to the hydrolysis of the vinyl ether by participating in two reactions. Firstly, they may function as a general acid to protonate the Asp35 carboxylate prior to isochorismate protonation; secondly, one of the catalytic waters may be activated by the ionizable side chain of Asp35 to perform a nucleophilic attack on the intermediate carbocation/oxocarbonium ion. The positions of the waters are both significantly affected by the mutation of Asp35 and Lys118. The structural, biochemical and MD results reveal the residues that are involved in substrate binding and provide clues towards defining a possible mechanism. Structural insight into the ISC domain of VibB from Vibrio cholerae at atomic resolution: a snapshot just before the enzymatic reaction.,Liu S, Zhang C, Li N, Niu B, Liu M, Liu X, Wei T, Zhu D, Huang Y, Xu S, Gu L Acta Crystallogr D Biol Crystallogr. 2012 Oct;68(Pt 10):1329-38. Epub 2012 Sep, 13. PMID:22993087[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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