Cytochrome 6558 of the gram-positive bacterium Bacillus subtilis is the membrane anchor subunit of the succinate:quinone oxidoreductase of the citric acid cycle. The cytochrome consists of the SdhC polypeptide (202 residues) and two protoheme IX groups that function in transmembrane electron transfer to menaquinone. The general structure of the cytochrome is known from extensive experimental studies and by comparison to Wolinella succinogenes fumarate reductase for which the X-ray crystal structure has been determined. Solution state NMR can potentially be used to identify the quinone binding site(s) and study, e.g. redox-linked, dynamics of cytochrome b(558). In this work we present an efficient procedure for the isolation of preparative amounts of isotopically labeled B. subtilis cytochrome 6558 produced in Escherichia coli. We have also evaluated several detergents suitable for NMR for their effectiveness in maintaining the cytochrome solubilized and intact for days at room temperature. (C) 2011 Elsevier Inc. All rights reserved.