Open AccessStructure of XC6422 from Xanthomonas campestris at 1.6 Å resolution: a small serine α/β‐hydrolase
Author(s) -
Yang ChaoYu,
Chin KoHsin,
Chou ChiaCheng,
Wang Andrew H.J.,
Chou ShanHo
Publication year - 2006
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309106016265
Subject(s) - catalytic triad , serine hydrolase , hydrolase , oxyanion hole , xanthomonas campestris , serine , pathovar , active site , esterase , protein structure , protein quaternary structure , stereochemistry , biology , biochemistry , protein data bank (rcsb pdb) , chemistry , protein subunit , enzyme , bacteria , genetics , pseudomonas , pseudomonadaceae , gene
XC6422 is a conserved hypothetical protein from Xanthomonas campestris pathovar campestris (Xcc), a Gram‐negative yellow‐pigmented pathogenic bacterium that causes black rot, one of the major worldwide diseases of cruciferous crops. The protein consists of 220 amino acids and its structure has been determined to 1.6 Å resolution using the multi‐wavelength anomalous dispersion (MAD) method. Although it has very low sequence identity to protein sequences in the PDB (less than 20%), the determined structure nevertheless shows that it belongs to the superfamily of serine α/β‐hydrolases, with an active site that is fully accessible to solvent owing to the absence of a lid domain. Modelling studies with the serine esterase inhibitor E600 indicate that XC6422 adopts a conserved Ser‐His‐Asp catalytic triad common to this superfamily and has a preformed oxyanion hole for catalytic activation. These structural features suggest that XC6422 is most likely to be a hydrolase active on a soluble ester or a small lipid. An extra strand preceding the first β‐strand in the canonical α/β‐hydrolase fold leads to extensive subunit interactions between XC6422 monomers, which may explain why XC6422 crystals of good diffraction quality can grow to dimensions of up to 1.5 mm in a few days.