THE UNIVERSAL STRESS PROTEIN, USPA, OF ESCHERICHIA-COLI IS PHOSPHORYLATED IN RESPONSE TO STASIS

Transcriptional induction of the uspA gene of Escherichia coli occurs whenever conditions cause growth arrest and cells deficient in UspA su rvive poorly in stationary phase. We demonstrate that the product of u spA is a serine and threonine phosphoprotein. In vivo, three isoforms of UspA were detected, two of which were phosphorylated as determined by alkaline phosphatase treatment; in vitro, phosphorylation with [y-P -32]ATP yielded two radioactive UspA isoforms. The phosphorylated isof orms were barely visible in growing cells but one increased during sta rvation conditions causing growth arrest. This phosphorylation is depe ndent on the o591 gene, which encodes an autophosphorylating tyrosine phosphoprotein and which is involved in the synthesis or modification of six other proteins. In vitro, UspA undergoes a rapid and dynamic au tophosphorylation, as shown by chase experiments with GTP or ATP as ph osphate donors. (C) 1997 Academic Press Limited.