title: PhpA, a tyrosine phosphatase of Myxococcus xanthus, is involved in the production of exopolysaccharide.
abstract: Protein-tyrosine phosphorylation plays a significant role in multiple cellular functions in bacteria. Bacterial tyrosine phosphatases catalyse the dephosphorylation of tyrosyl-phosphorylated proteins. Myxococcus xanthus PhpA shares homology with DNA polymerase and histidinol phosphatase family members. Recombinant His-tagged PhpA requires Mn(2+) or Co(2+) for phosphatase activity, and shows strict specificity for phosphorylated tyrosine residues. The k(m) values of PhpA for p-nitrophenyl phosphate (pNPP) and phosphotyrosine peptide, RRLIEDAEpYAARG, were 803 and 139 µM, respectively. The phosphatase activity of PhpA was inhibited by sodium orthovanadate with a k(i) of 33 µM. phpA gene expression was observed under both vegetative and developmental conditions, but peaked during late fruiting body formation. A phpA mutant exhibited an elevated level of tyrosine phosphorylation of a 79 kDa protein and cytoplasmic tyrosine kinase, BtkA. In M. xanthus, exopolysaccharide (EPS) is essential for cell-cell adhesion and fruiting body formation. phpA mutant cells exhibited enhanced capacity for cell-cell agglutination in agglutination buffer. Under starvation conditions, phpA mutation caused early aggregation and sporulation. The EPS production assay showed that the phpA mutant produced an increased amount of EPS in comparison with the wild-type. These results indicate that PhpA may negatively regulate the production of EPS in M. xanthus.
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Mori
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Miri
authors.initials: M
authors.lastname: Maeda
authors.affiliation: Department of Bioscience and Biotechnology, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Takegawa
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kimura
mesh_terms: D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D009154:Mutation; D016941:Myxococcus xanthus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D011134:Polysaccharides / Q000096:biosynthesis*; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D013171:Spores, Bacterial / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D011134:Polysaccharides; D017027:Protein Tyrosine Phosphatases