2jbw

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spinqualitylabelsall models 2jbw, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURE OF THE 2,6-DIHYDROXY-PSEUDO-OXYNICOTINE HYDROLASE.

Overview

The enzyme 2,6-dihydroxy-pseudo-oxynicotine hydrolase from the, nicotine-degradation pathway of Arthrobacter nicotinovorans was, crystallized and the structure was determined by an X-ray diffraction, analysis at 2.1 A resolution. The enzyme belongs to the, alpha/beta-hydrolase family as derived from the chain-fold and from the, presence of a catalytic triad with its oxyanion hole at the common, position. This relationship assigns a pocket lined by the catalytic triad, as the active center. The asymmetric unit contains two C(2)-symmetric, dimer molecules, each adopting a specific conformation. One dimer forms a, more spacious active center pocket and the other a smaller one, suggesting, an induced-fit. All of the currently established C-C bond cleaving, alpha/beta-hydrolases are from bacterial meta-cleavage pathways for the, degradation of aromatic compounds and cover their active center with a 40, residue lid placed between two adjacent strands of the beta-sheet. In, contrast, the reported enzyme shields its active center with a 110 residue, N-terminal domain, which is absent in the meta-cleavage hydrolases. Since, neither the substrate nor an analogue could be bound in the crystals, the, substrate was modeled into the active center using the oxyanion hole as a, geometric constraint. The model was supported by enzymatic activity data, of 11 point mutants and by the two dimer conformations suggesting an, induced-fit. Moreover, the model assigned a major role for the large, N-terminal domain that is specific to the reported enzyme. The proposal is, consistent with the known data for the meta-cleavage hydrolases although, it differs in that the reaction does not release alkenes but a, hetero-aromatic compound in a retro-Friedel-Crafts acylation. Because the, hydrolytic water molecule can be assigned to a geometrically suitable site, that can be occupied in the presence of the substrate, the catalytic triad, may not form a covalent acyl-enzyme intermediate but merely support a, direct hydrolysis.

About this Structure

2JBW is a Single protein structure of sequence from Arthrobacter nicotinovorans with NA as ligand. Structure known Active Site: TRI. Full crystallographic information is available from OCA.

Reference

Structure and action of a C-C bond cleaving alpha/beta-hydrolase involved in nicotine degradation., Schleberger C, Sachelaru P, Brandsch R, Schulz GE, J Mol Biol. 2007 Mar 23;367(2):409-18. Epub 2006 Dec 30. PMID:17275835

Page seeded by OCA on Mon Nov 5 13:51:12 2007