Pph1 from Myxococcus xanthus is a protein phosphatase involved in vegetative growth and development.
Myxococcus xanthus is a Gram-negative bacterium with a complex life cycle that includes vegetative swarming on rich medium and, upon starvation, aggregation to form fruiting bodies containing spores. Both of these behaviours require multiple Ser/Thr protein kinases. In this paper, we report the first Ser/Thr protein phosphatase gene, pph1, from M. xanthus. DNA sequence analysis of pph1 indicates that it encodes a protein of 254 residues (Mr = 28 308) with strong homology to eukaryotic PP2C phosphatases and that it belongs to a new group of bacterial protein phosphatases that are distinct from bacterial PP2C phosphatases such as RsbU, RsbX and SpoIIE. Recombinant His-tagged Pph1 was purified from Escherichia coli and shown to have Mn2+ or Mg2+ dependent, okadaic acid-resistant phosphatase activity on a synthetic phosphorylated peptide, RRA(pT)VA, indicating that Pph1 is a PP2C phosphatase. Pph1-expression was observed under both vegetative and developmental conditions, but peaked during early aggregation. A pph1 null mutant showed defects during late vegetative growth, swarming and glycerol spore formation. Under starvation-induced developmental conditions, the mutant showed reduced aggregation and failure to form fruiting bodies with viable spores. Using the yeast two-hybrid system, we have observed a strong interaction between Pph1 and the M. xanthus protein kinase Pkn5, a negative effector of development. These results suggest a functional link between a Pkn2-type protein kinase and a PP2C phosphatase.
Treuner-Lange
A
A
Department of Molecular and Cell Biology, 401 Barker Hall, University of California, Berkeley, CA 94720-3204, USA.
Ward
M J
MJ
Zusman
D R
DR
D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D007763:Lac Operon; D009154:Mutation; D016941:Myxococcus xanthus / Q000201:enzymology* / Q000254:growth & development; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D017931:DNA Primers; D011994:Recombinant Proteins; D010749:Phosphoprotein Phosphatases