Cloning, expression, crystallization and preliminary X-ray characterization of cytochrome c₅₅₂ from a moderate thermophilic bacterium, Hydrogenophilus thermoluteolus

The amino-acid sequence of cytochrome c₅₅₂ (PH c₅₅₂) from a moderately thermophilic bacterium, Hydrogenophilus thermoluteolus, was more than 50% identical to that of cytochrome c from an extreme thermophile, Hydrogenobacter thermophilus (HT c₅₅₂), and from a mesophile, Pseudomonas aeruginosa (PA c₅₅₁). The PH c₅₅₂ gene was overexpressed as a correctly processed holoprotein in the Escherichia coli periplasm. The overexpressed PH c₅₅₂ has been crystallized by vapour diffusion from polyethylene glycol 4000 pH 6.5. The crystals belong to space group C222₁, with unit-cell parameters a = 48.98, b = 57.99, c = 56.20 Å. The crystals diffract X-rays to around 2.1 Å resolution.