Open AccessPreliminary X‐ray crystallographic studies of the catalytic subunit of Escherichia coli AHAS II with its cofactors
Author(s) -
Niu Xuhui,
Liu Xiang,
Zhou Yanfei,
Niu Congwei,
Xi Zhen,
Su XiaoDong
Publication year - 2011
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309111008839
Subject(s) - escherichia coli , cofactor , protein subunit , crystallography , catalysis , x ray , chemistry , stereochemistry , biochemistry , enzyme , physics , gene , quantum mechanics
Acetohydroxyacid synthase (AHAS) is the first common enzyme in the branched‐chain amino‐acid biosynthesis pathway and is the target of several classes of commercial herbicides. In this study, the Escherichia coli ilv G gene that encodes the catalytic subunit of AHAS II was cloned into the pET28a vector and expressed in soluble form at high levels in E. coli strain BL21 (DE3) cells. The protein was purified using Ni 2+ ‐chelating chromatography followed by size‐exclusion chromatography. The catalytic subunit of E. coli AHAS II was cocrystallized with its cofactors Mg 2+ , FAD and ThDP using the sitting‐drop vapour‐diffusion method and the crystals diffracted to 2.80 Å resolution.