Protein Phosphorylation in Rhodomicrobium vannielii

Abstract

Summary: Analysis of cell extracts of Rhodomicrobium vannielii continuously labelled with [32P]orthophos-phate revealed that at least 25 polypeptides were phosphorylated, including abundant species of M r 88000, 66000, 55000 and 12700, and that the phosphate groups were ester-linked to serine, threonine and tyrosine. Pulse labelling with [32P]orthophosphate indicated that the protein phosphorylation profile was dependent upon the growth stage of the culture. Comparison of phosphopolypeptide profiles of reproductive and swarmer cells suggested that protein phosphorylation was drastically reduced in the swarmer cell. However, during the course of differentiation phosphopolypeptides became increasingly abundant, particularly two species of M r 55000 and 86000. Although protein kinase activities could be detected in vitro, there was little similarity between the in vitro pattern of phosphorylated polypeptides and that obtained in vivo.