A protein required for secretion of cholera toxin through the outer membrane of Vibrio cholerae

A gene essential for the secretion of cholera toxin from the periplasm of Vibrio cholerae into the extracellular medium has been isolated and its nucleotide sequence determined. It encodes a cytoplasmic protein of 56 kDa that exhibits a high degree of similarity to gene products required for extracellular protein secretion in several other Gram− organisms. Sequence similarities in its potential ATP-binding site suggest that the protein may act as an energy provider or signal transducer in the process of extracellular secretion.