F0 cysteine, bCys21, in the Escherichia coli ATP synthase is involved in regulation of potassium uptake and molecular hydrogen production in anaerobic conditions

The single cysteine in the b subunit of the membranous F-0 sector and the 19 cysteines in extramembranous F-1 sector of the Escherichia coli ATP synthase were replaced by alanine. When cells were grown under anaerobic conditions on glucose, the k(cat) for ATP hydrolysis of membrane vesicles containing the bCys21Ala mutant enzyme, but not enzymes with other cysteine replacements, was lower, while ATP-driven H+ pumping was unchanged. However, the ATP-dependent increase in the number of accessible thiol groups in membrane vesicles was negated. Furthermore, K+ uptake and molecular hydrogen production by whole cells and protoplasts was greatly decreased. These results indicate a role for the F-0 subunit bCys21 in the functionality of F0F1 and coupling to other membranous activities under fermentative conditions.