1xys

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spinqualitylabelsall models 1xys, resolution 2.5Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CATALYTIC CORE OF XYLANASE A E246C MUTANT

Overview

BACKGROUND: Sequence alignment suggests that xylanases evolved from two, ancestral proteins and therefore can be grouped into two families, designated F and G. Family F enzymes show no sequence similarity with any, known structure and their architecture is unknown. Studies of an inactive, enzyme-substrate complex will help to elucidate the structural basis of, binding and catalysis in the family F xylanases. RESULTS: We have, therefore determined the crystal structure of the catalytic domain of a, family F enzyme, Pseudomonas fluorescens subsp. cellulosa xylanase A, at, 2.5 A resolution and a crystallographic R-factor of 0.20. The structure, was solved using an engineered catalytic core in which the nucleophilic, glutamate was replaced by a cysteine. As expected, this yielded both, high-quality mercurial derivatives and an inactive enzyme which enabled, the preparation of the inactive enzyme-substrate complex in the crystal., We show that family F xylanases are eight-fold alpha/beta-barrels (TIM, barrels) with two active-site glutamates, one of which is the nucleophile, and the other the acid-base. Xylopentaose binds to five subsites A-E with, the cleaved bond between subsites D and E. Ca2+ binding, remote from the, active-site glutamates, stabilizes the structure and may be involved in, the binding of extended substrates. CONCLUSIONS: The architecture of P., fluorescens subsp. cellulosa has been determined crystallographically to, be a commonly occurring enzyme fold, the eight-fold alpha/beta-barrel., Xylopentaose binds across the carboxy-terminal end of the, alpha/beta-barrel in an active-site cleft which contains the two catalytic, glutamates.

About this Structure

1XYS is a Single protein structure of sequence from Cellvibrio japonicus with CA as ligand. Active as Endo-1,4-beta-xylanase, with EC number 3.2.1.8 Full crystallographic information is available from OCA.

Reference

Structure of the catalytic core of the family F xylanase from Pseudomonas fluorescens and identification of the xylopentaose-binding sites., Harris GW, Jenkins JA, Connerton I, Cummings N, Lo Leggio L, Scott M, Hazlewood GP, Laurie JI, Gilbert HJ, Pickersgill RW, Structure. 1994 Nov 15;2(11):1107-16. PMID:7881909

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