Regulation of proline utilization in Salmonella typhimurium: Autogenous regulation by a membrane-associated dehydrogenase

Abstract

Salmonella typhimurium and Escherichia coli can utilize proline as a sole carbon or nitrogen source. Proline utilization requires the expression of the two genes in the put operon: the putP gene, which encodes proline permease, and the putA gene, which encodes a bifunctional membrane-associated dehydrogenase that degrades proline to glutamate. The PutA protein also autogenously regulates transcription of the put operon. Induction of the put operon requires proline, oxygen (or another terminal electron acceptor), and available membrane binding sites. A simple model explains the regulation: under inducing conditions the PutA protein binds to the membrane where it is enzymatically active, but when the intracellular concentration of proline is low or when few functional membrane binding sites are available, the PutA protein accumulates in the cytoplasm where it represses transcription of the put operon. This change in cellular localization seems to be at least partly induced by changes in the redox state of PutA protein. This unique autoregulatory mechanism allows induction of the put operon only when both the inducer, high intracellular proline concentration, and functional membrane sites required for enzyme activity are available.U of I OnlyETDs are only available to UIUC Users without author permissio