Succinate dehydrogenase mutants of Bacillus subtilis lacking covalently bound flavin in the flavoprotein subunit

Succinate dehydrogenase consists of two unequal subunits; Fp and Ip. An FAD group is covalently linked to a histidyl residue in the Fp subunit. The mechanism by which flavin is attached to protein is not known. Covalently bound flavin was studied in wild-type and succinate-dehydrogenase-negative Bacillus subtilis. The Fp subunit of succinate dehydrogenase was found to be the only (major) flavinylated protein in the cell. Mutants lacking covalently bound flavin and still containing the Fp polypeptide are described. It is shown that the flavin is not essential for assembly and membrane binding of succinate dehydrogenase in B. subtilis.