Crystallization and preliminary X-ray crystallographic analysis of a periplasmic tetrahaem flavocytochrome c3 from Shewanella frigidimarina NCIMB400 which has fumarate reductase activity

The fumarate reductase of Echerichia coli and other bacteria is a membrane-bound enzyme consisting, of four subunits. A soluble periplasmic 64 kDa tetrahaem flavocytochrome c(3), from Shewanella frigidimarina NCIMB400 which possesses a catalytic fumarate reductase activity has been crystallized. The crystals belong to space group P2(1)2(1)2(1) with unit-cell parameters a = 72.4, b = 110.1, c = 230.2 Angstrom. Assuming a molecular dimer in the asymmetric unit, the crystals contain 65% solvent and, when cryocooled to 100 K, the crystals diffract to at least 3.0 Angstrom resolution. The crystals, however, display an inherent lack of isomorphism and the plausibility of a MAD phasing experiment has therefore been investigated by measuring the iron K absorption edge from a single crystal.