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Rajagopal, L, Clancy, A and Rubens, CE (2003) A eukaryotic type serine/threonine kinase and phosphatase in Streptococcus agalactiae reversibly phosphorylate an inorganic pyrophosphatase and affect growth, cell segregation, and virulence. J. Biol. Chem. 278:14429-41


Protein phosphorylation is essential for the regulation of cell growth, division, and differentiation in both prokaryotes and eukaryotes. Signal transduction in prokaryotes was previously thought to occur primarily by histidine kinases, involved in two-component signaling pathways. Lately, bacterial homologues of eukaryotic-type serine/threonine kinases and phosphatases have been found to be necessary for cellular functions such as growth, differentiation, pathogenicity, and secondary metabolism. The Gram-positive bacteria Streptococcus agalactiae (group B streptococci, GBS) is an important human pathogen. We have identified and characterized a eukaryotic-type serine/threonine protein kinase (Stk1) and its cognate phosphatase (Stp1) in GBS. Biochemical assays revealed that Stk1 has kinase activity and localizes to the membrane and that Stp1 is a soluble protein with manganese-dependent phosphatase activity on Stk1. Mutations in these genes exhibited pleiotropic effects on growth, virulence, and cell segregation of GBS. Complementation of these mutations restored the wild type phenotype linking these genes to the regulation of various cellular processes in GBS. In vitro phosphorylation of cell extracts from wild type and mutant strains revealed that Stk1 is essential for phosphorylation of six GBS proteins. We have identified the predominant endogenous substrate of both Stk1 and Stp1 as a manganese-dependent inorganic pyrophosphatase (PpaC) by liquid chromatography/tandem mass spectrometry. These results suggest that these eukaryotic-type enzymes regulate pyrophosphatase activity and other cellular functions of S. agalactiae.


PubMed Online version:10.1074/jbc.M212747200


Alkaline Phosphatase/metabolism; Alleles; Amino Acid Sequence; Animals; Chromatography, Liquid; Cyclin-Dependent Kinases; DNA/metabolism; Electrophoresis, Gel, Two-Dimensional; Female; Genetic Complementation Test; Glutathione Transferase/metabolism; Inorganic Pyrophosphatase; Manganese/metabolism; Mass Spectrometry; Microscopy, Electron; Molecular Sequence Data; Mutagenesis, Site-Directed; Mutation; Open Reading Frames; Phenotype; Phosphorylation; Protein-Serine-Threonine Kinases/chemistry; Protein-Serine-Threonine Kinases/metabolism; Pyrophosphatases/metabolism; Rats; Rats, Sprague-Dawley; Recombinant Fusion Proteins/metabolism; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Streptococcus agalactiae/enzymology; Time Factors; Transcription, Genetic



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0004674: protein serine/threonine kinase activity



Figure 2 shows that Stk1 phosphorylates at serine and threonine residues

CACAO 5342


GO:0016791: phosphatase activity



Figure 3 shows Stp1 hydrolyzing pNP-phosphate into pNP

CACAO 5343

See also


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