A FUNCTIONAL CHIMERIC MEMBRANE SUBUNIT OF AN ION-TRANSLOCATING ATPASE

A chimeric transport protein was made by expression of a fusion of the arsB genes from Escherichia coli plasmid R773 and Staphylococcus aure us plasmid pI258. The two genes were fused to encode a functional prot ein with first eight membrane spanning alpha-helices of the S. aureus and the last four helices of the E. coli protein. The hybrid protein p rovided arsenite resistance and transport. When an arsA gene was expre ssed in trans with the ArsB proteins encoded by the R773, pI258 and fu sion genes, arsenite efflux was dependent on chemical but not electroc hemical energy. The Ars system is hypothesized to be a novel transport system that functions as a primary ATP-driven pump or a secondary car rier, depending on the subunit composition of the complex.