Overproduction and preliminary crystallographic study of a human kynurenine aminotransferase II homologue from Pyrococcus horikoshii OT3
The Pyrococcus horikoshii OT3 genome contains a gene encoding a human kynurenine aminotransferase II (KAT II) homologue, which consists of 428 amino‐acid residues and shows an amino‐acid sequence identity of 30% to human KAT II. This gene was overexpressed in Escherichia coli and the recombinant protein (Ph‐KAT II) was purified. Gel‐filtration chromatography showed that Ph‐KAT II exists as a homodimer. Ph‐KAT II exhibited enzymatic activity that catalyzes the transamination of l‐kynurenine to produce kynurenic acid. Crystals of Ph‐KAT II were grown using the sitting‐drop vapour‐diffusion method and native X‐ray diffraction data were collected to 2.2 Å resolution using synchrotron radiation from station BL44XU at SPring‐8. The crystals belong to the centred orthorhombic space group C2221, with unit‐cell parameters a = 71.75, b = 86.84, c = 137.30 Å. Assuming one molecule per asymmetric unit, the V M value was 2.19 Å3 Da−1 and the solvent content was 43.3%.
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