Paralogous genes encoding transport proteins in microbial genomes.

The largest superfamilies of prokaryotic genes encode transport proteins, but many transporters are encoded by orphan genes or those that comprise very small families. We have analyzed eighteen completely sequenced prokaryotic genomes for paralogous transport systems and have thereby identified 76 permease families. In this short review, we present and discuss the paralogues in some of these families and interpret the most prominent results, particularly those relevant to the largest permease superfamilies.