Transporter's evolution and carbohydrate metabolic clusters.

The yiaQRS genes of Escherichia coli K-12 are involved in carbohydrate metabolism. Clustering of homologous genes was found throughout several unrelated bacteria. Strikingly, all four bacterial transport protein classes were found, conserving transport function but not mechanism. It appears that during evolution the ability to transport, phosphorylate and metabolize substrates of unknown identity have been conserved. However, the transporter classes have been swapped. This probably demonstrates the subtlety of transport-protein evolution.