Phosphotransfer signal transduction between two regulatory factors involved in the osmoregulated <i>kdp</i> operon in <i>Escherichia coli</i>

Abstract

The proteins KdpD and KdpE are regulatory factors critically involved in the osmotic regulation of the kdpABC operon that is responsible for a high-affinity transport system in Escherichia coli. In this study, we obtained biochemical evidence supporting the view that the KdpD protein is a sensory protein kinase that exhibits autophosphorylation and KdpE-phosphotransfer characteristics. During the course of such studies we established a procedure for purifying the KdpE protein in large quantities. We also developed a procedure for preparing cytoplasmic membrane enriched with the KdpD protein that exhibits in vitro ability with regard to phosphorylation of KdpE protein.