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spinqualitylabelsall models 1c0n, resolution 2.8Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CSDB PROTEIN, NIFS HOMOLOGUE

Overview

Escherichia coli CsdB, a NifS homologue with a high specificity for, L-selenocysteine, is a pyridoxal 5'-phosphate (PLP)-dependent dimeric, enzyme that belongs to aminotransferases class V in fold-type I of PLP, enzymes and catalyzes the decomposition of L-selenocysteine into selenium, and L-alanine. The crystal structure of the enzyme has been determined by, the X-ray crystallographic method of multiple isomorphous replacement and, refined to an R-factor of 18.7% at 2.8 A resolution. The subunit structure, consists of three parts: a large domain of an alpha/beta-fold containing a, seven-stranded beta-sheet flanked by seven helices, a small domain, containing a four-stranded antiparallel beta-sheet flanked by three, alpha-helices, and an N-terminal segment containing two alpha-helices. The, overall fold of the subunit is similar to those of the enzymes belonging, to the fold-type I family represented by aspartate aminotransferase., However, CsdB has several structural features that are not observed in, other families of the enzymes. A remarkable feature is that an alpha-helix, in the lobe extending from the small domain to the large domain in one, subunit of the dimer interacts with a beta-hairpin loop protruding from, the large domain of the other subunit. The extended lobe and the protruded, beta-hairpin loop form one side of a limb of each active site in the, enzyme. The most striking structural feature of CsdB lies in the location, of a putative catalytic residue; the side chain of Cys364 on the extended, lobe of one subunit is close enough to interact with the gamma-atom of a, modeled substrate in the active site of the subunit. Moreover, His55 from, the other subunit is positioned so that it interacts with the gamma- or, beta-atom of the substrate and may be involved in the catalytic reaction., This is the first report on three-dimensional structures of NifS, homologues.

About this Structure

1C0N is a Single protein structure of sequence from Escherichia coli with PLP and ACY as ligands. Full crystallographic information is available from OCA.

Reference

Structure of a NifS homologue: X-ray structure analysis of CsdB, an Escherichia coli counterpart of mammalian selenocysteine lyase., Fujii T, Maeda M, Mihara H, Kurihara T, Esaki N, Hata Y, Biochemistry. 2000 Feb 15;39(6):1263-73. PMID:10684605

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