Wide distribution of homologs of Escherichia coli Kdp K+-ATPase among gram-negative bacteria.

We used Southern blotting to screen a variety of bacterial genes for homology to the kdp genes of Escherichia coli, genes that encode an ATP-driven K+ transport system. We found that most enterobacteria have sequences homologous to those of the three kdp structural genes and the kdpD regulatory gene. A number of distantly related species, including some cyanobacteria, have sequences homologous to those of the structural genes but not the regulatory gene. In all cases only a single region of homology was found. These results suggest that ATP-driven transport systems similar to the Kdp system in structure and regulation are found in many enteric organisms. In other gram-negative organisms, the ATPase is more divergent, retaining good homology at the DNA level only to the highly conserved phosphorylated subunit of the ATPase.