Escherichia coli formate dehydrogenase mutants with altered selenopolymer profiles.

Four classes of Escherichia coli mutants deficient in either or both of their anaerobic selenium-containing formate dehydrogenases (FDH) were isolated. A class I mutant devoid of FDHH activity specifically linked to benzyl viologen (BV) produced a small amount of the FDHH 80,000 dalton selenopeptide. Three class II mutants were deficient in FDHN activity specifically linked to phenazine methosulfate (PMS) and exhibited a selenopeptide "doublet" rather than the FDHN 110,000 dalton selenosubunit. Three class III mutants were selenium incorporation deficient and did not exhibit either FDH activity or 75Se-labeled selenopolymers. A class IV mutant was devoid of PMS-linked FDHN activity; neither its FDHN 110,000 dalton selenosubunit nor its BV-linked FDHH activity was fully regulated by nitrate.