AN AEROMONAS-SALMONICIDA GENE WHICH INFLUENCES A-PROTEIN EXPRESSION IN ESCHERICHIA-COLI ENCODES A PROTEIN CONTAINING AN ATP-BINDING CASSETTE AND MAPS BESIDE THE SURFACE ARRAY PROTEIN GENE

A conserved Aeromonas salmonicida gene (abcA) affecting expression of the surface array protein gene (vapA) in Escherichia coli was identifi ed. The 924-bp gene starts 205 bp after vapA and codes for a protein w ith a deduced molecular weight (M(r)) of 34,015 containing an N-termin al P-loop and significant homology to the ATP-binding cassette transpo rt protein superfamily. AbcA was identified by sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) by using T7 polymerase e xpression and DNA-directed translation and was copurified with the sar kosyl-soluble cytoplasmic membrane fraction. The protein displayed abe rrant migration during SDS-PAGE. A lacZ fusion containing 128 bp of up stream sequence and 387 bases in the 5' end of abcA was constructed, a nd the beta-galactosidase activity of the abcA-lacZ fusion gene was sh own to be similar in E. coli and A. salmonicida. The 130,000-M(r) AbcA -LacZ fusion protein was purified, and by using an ATP affinity column , the 129 AbcA N-terminal P-loop-containing residues were shown to bin d ATP.