Eukaryotic-type serine/threonine protein kinase StkP is a global regulator of gene expression in Streptococcus pneumoniae
Jazyk angličtina Země Spojené státy americké Médium print-electronic
Typ dokumentu časopisecké články, práce podpořená grantem
PubMed
17416671
PubMed Central
PMC1913385
DOI
10.1128/jb.01616-06
PII: JB.01616-06
Knihovny.cz E-zdroje
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- delece genu MeSH
- eukaryotické buňky enzymologie MeSH
- fenotyp MeSH
- koncentrace vodíkových iontů MeSH
- mikrobiální viabilita účinky léků genetika MeSH
- mutace MeSH
- osmotický tlak MeSH
- oxidační stres MeSH
- peroxid vodíku farmakologie MeSH
- polymerázová řetězová reakce s reverzní transkripcí MeSH
- protein-serin-threoninkinasy genetika metabolismus MeSH
- regulace genové exprese u bakterií * MeSH
- sekvenční analýza hybridizací s uspořádaným souborem oligonukleotidů MeSH
- Streptococcus pneumoniae enzymologie genetika růst a vývoj MeSH
- testy genetické komplementace MeSH
- vysoká teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- bakteriální proteiny MeSH
- peroxid vodíku MeSH
- protein-serin-threoninkinasy MeSH
Signal transduction pathways in both prokaryotes and eukaryotes utilize protein phosphorylation as a key regulatory mechanism. Recent studies have proven that eukaryotic-type serine/threonine protein kinases (Hank's type) are widespread in many bacteria, although little is known regarding the cellular processes they control. In this study, we have attempted to establish the role of a single eukaryotic-type protein kinase, StkP of Streptococcus pneumoniae, in bacterial survival. Our results indicate that the expression of StkP is important for the resistance of S. pneumoniae to various stress conditions. To investigate the impact of StkP on this phenotype, we compared the whole-genome expression profiles of the wild-type and DeltastkP mutant strains by microarray technology. This analysis revealed that StkP positively controls the transcription of a set of genes encoding functions involved in cell wall metabolism, pyrimidine biosynthesis, DNA repair, iron uptake, and oxidative stress response. Despite the reduced transformability of the stkP mutant, we found that the competence regulon was derepressed in the stkP mutant under conditions that normally repress natural competence development. Furthermore, the competence regulon was expressed independently of exogenous competence-stimulating peptide. In summary, our studies show that a eukaryotic-type serine/threonine protein kinase functions as a global regulator of gene expression in S. pneumoniae.
Zobrazit více v PubMed
Alloing, G., B. Martin, C. Granadel, and J. P. Claverys. 1998. Development of competence in Streptococcus pneumoniae: pheromone autoinduction and control of quorum sensing by the oligopeptide permease. Mol. Microbiol. 29:75-83. PubMed
Aravind, L., and E. V. Koonin. 1998. The HD domain defines a new superfamily of metal-dependent phosphohydrolases. Trends Biochem. Sci. 23:469-472. PubMed
Bateman, A., and M. Bycroft. 2000. The structure of a LysM domain from E. coli membrane-bound lytic murein transglycosylase D (MltD). J. Mol. Biol. 299:1113-1119. PubMed
Boitel, B., M. Ortiz-Lombardia, R. Duran, F. Pompeo, S. T. Cole, C. Cervenansky, and P. M. Alzari. 2003. PknB kinase activity is regulated by phosphorylation in two Thr residues and dephosphorylation by PstP, the cognate phospho-Ser/Thr phosphatase, in Mycobacterium tuberculosis. Mol. Microbiol. 49:1493-1508. PubMed
Bolzán, A. D., and M. S. Bianchi. 2001. Genotoxicity of streptonigrin: a review. Mutat. Res. 488:25-37. PubMed
Brown, J. S., S. M. Gilliland, and D. W. Holden. 2001. A Streptococcus pneumoniae pathogenicity island encoding an ABC transporter involved in iron uptake and virulence. Mol. Microbiol. 40:572-585. PubMed
Brown, J. S., S. M. Gilliland, J. Ruiz-Albert, and D. W. Holden. 2002. Characterization of Pit, a Streptococcus pneumoniae iron uptake ABC transporter. Infect. Immun. 70:4389-4398. PubMed PMC
Campbell, E. A., S. Y. Choi, and H. R. Masure. 1998. A competence regulon in Streptococcus pneumoniae revealed by genomic analysis. Mol. Microbiol. 27:929-939. PubMed
Canvin, J. R., J. C. Paton, G. J. Boulnois, P. W. Andrew, and T. J. Mitchell. 1997. Streptococcus pneumoniae produces a second haemolysin that is distinct from pneumolysin. Microb. Pathog. 22:129-132. PubMed
Cheng, Q., E. A. Campbell, A. M. Naughton, S. Johnson, and H. R. Masure. 1997. The com locus controls genetic transformation in Streptococcus pneumoniae. Mol. Microbiol. 23:683-692. PubMed
Chia, J. S., Y. Y. Lee, P. T. Huang, and J. Y. Chen. 2001. Identification of stress-responsive genes in Streptococcus mutans by differential display reverse transcription-PCR. Infect. Immun. 69:2493-2501. PubMed PMC
Claverys, J. P., and L. S. Havarstein. 2002. Extracellular-peptide control of competence for genetic transformation in Streptococcus pneumoniae. Front. Biosci. 7:d1798-d1814. PubMed
Cozzone, A. J. 2005. Role of protein phosphorylation on serine/threonine and tyrosine in the virulence of bacterial pathogens. J. Mol. Microbiol. Biotechnol. 9:198-213. PubMed
Curry, J. M., R. Whalan, D. M. Hunt, K. Gohil, M. Strom, L. Rickman, M. J. Colston, S. J. Smerdon, and R. S. Buxton. 2005. An ABC transporter containing a forkhead-associated domain interacts with a serine-threonine protein kinase and is required for growth of Mycobacterium tuberculosis in mice. Infect. Immun. 73:4471-4477. PubMed PMC
Dagkessamanskaia, A., M. Moscoso, V. Henard, S. Guiral, K. Overweg, M. Reuter, B. Martin, J. Wells, and J. P. Claverys. 2004. Interconnection of competence, stress and CiaR regulons in Streptococcus pneumoniae: competence triggers stationary phase autolysis of ciaR mutant cells. Mol. Microbiol. 51:1071-1086. PubMed
Dasgupta, A., P. Datta, M. Kundu, and J. Basu. 2006. The serine/threonine kinase PknB of Mycobacterium tuberculosis phosphorylates PBPA, a penicillin-binding protein required for cell division. Microbiology 152:493-504. PubMed
De Las Rivas, B., J. L. Garcia, R. Lopez, and P. Garcia. 2002. Purification and polar localization of pneumococcal LytB, a putative endo-β-N-acetylglucosaminidase: the chain-dispersing murein hydrolase. J. Bacteriol. 184:4988-5000. PubMed PMC
Echenique, J., A. Kadioglu, S. Romao, P. W. Andrew, and M. C. Trombe. 2004. Protein serine/threonine kinase StkP positively controls virulence and competence in Streptococcus pneumoniae. Infect. Immun. 72:2434-2437. PubMed PMC
Ehrenshaft, M., P. Bilski, M. Y. Li, C. F. Chignell, and M. E. Daub. 1999. A highly conserved sequence is a novel gene involved in de novo vitamin B6 biosynthesis. Proc. Natl. Acad. Sci. USA 96:9374-9378. PubMed PMC
Fabret, C., and J. A. Hoch. 1998. A two-component signal transduction system essential for growth of Bacillus subtilis: implications for anti-infective therapy. J. Bacteriol. 180:6375-6383. PubMed PMC
Galyov, E. E., S. Hakansson, A. Forsberg, and H. Wolf-Watz. 1993. A secreted protein kinase of Yersinia pseudotuberculosis is an indispensable virulence determinant. Nature 361:730-732. PubMed
Gosink, K. K., E. R. Mann, C. Guglielmo, E. I. Tuomanen, and H. R. Masure. 2000. Role of novel choline binding proteins in virulence of Streptococcus pneumoniae. Infect. Immun. 68:5690-5695. PubMed PMC
Gourse, R. L., W. Ross, and T. Gaal. 2000. UPs and downs in bacterial transcription initiation: the role of the alpha subunit of RNA polymerase in promoter recognition. Mol. Microbiol. 37:687-695. PubMed
Guiral, S., V. Henard, C. Granadel, B. Martin, and J. P. Claverys. 2006. Inhibition of competence development in Streptococcus pneumoniae by increased basal-level expression of the ComDE two-component regulatory system. Microbiology 152:323-331. PubMed
Hendriksen, W. T., N. Silva, H. J. Bootsma, C. E. Blue, G. K. Paterson, A. R. Kerr, A. de Jong, O. P. Kuipers, P. W. Hermans, and T. J. Mitchell. 2007. Regulation of gene expression in Streptococcus pneumoniae by response regulator 09 is strain dependent. J. Bacteriol. 189:1382-1389. PubMed PMC
Hui, F. M., L. Zhou, and D. A. Morrison. 1995. Competence for genetic transformation in Streptococcus pneumoniae: organization of a regulatory locus with homology to two lactococcin A secretion genes. Gene 153:25-31. PubMed
Hussain, H., P. Branny, and E. Allan. 2006. A eukaryotic-type serine/threonine protein kinase is required for biofilm formation, genetic competence, and acid resistance in Streptococcus mutans. J. Bacteriol. 188:1628-1632. PubMed PMC
Jin, H., and V. Pancholi. 2006. Identification and biochemical characterization of a eukaryotic-type serine/threonine kinase and its cognate phosphatase in Streptococcus pyogenes: their biological functions and substrate identification. J. Mol. Biol. 357:1351-1372. PubMed
Jolly, L., F. Pompeo, J. van Heijenoort, F. Fassy, and D. Mengin-Lecreulx. 2000. Autophosphorylation of phosphoglucosamine mutase from Escherichia coli. J. Bacteriol. 182:1280-1285. PubMed PMC
Joris, B., S. Englebert, C. P. Chu, R. Kariyama, L. Daneo-Moore, G. D. Shockman, and J. M. Ghuysen. 1992. Modular design of the Enterococcus hirae muramidase-2 and Streptococcus faecalis autolysin. FEMS Microbiol. Lett. 70:257-264. PubMed
Kang, C. M., D. W. Abbott, S. T. Park, C. C. Dascher, L. C. Cantley, and R. N. Husson. 2005. The Mycobacterium tuberculosis serine/threonine kinases PknA and PknB: substrate identification and regulation of cell shape. Genes Dev. 19:1692-1704. PubMed PMC
Lange, R., C. Wagner, A. de Saizieu, N. Flint, J. Molnos, M. Stieger, P. Caspers, M. Kamber, W. Keck, and K. E. Amrein. 1999. Domain organization and molecular characterization of 13 two-component systems identified by genome sequencing of Streptococcus pneumoniae. Gene 237:223-234. PubMed
Lee, M. S., and D. A. Morrison. 1999. Identification of a new regulator in Streptococcus pneumoniae linking quorum sensing to competence for genetic transformation. J. Bacteriol. 181:5004-5016. PubMed PMC
Lu, Y., and R. L. Switzer. 1996. Evidence that the Bacillus subtilis pyrimidine regulatory protein PyrR acts by binding to pyr mRNA at three sites in vivo. J. Bacteriol. 178:5806-5809. PubMed PMC
Luo, P., H. Li, and D. A. Morrison. 2003. ComX is a unique link between multiple quorum sensing outputs and competence in Streptococcus pneumoniae. Mol. Microbiol. 50:623-633. PubMed
Luo, P., and D. A. Morrison. 2003. Transient association of an alternative sigma factor, ComX, with RNA polymerase during the period of competence for genetic transformation in Streptococcus pneumoniae. J. Bacteriol. 185:349-358. PubMed PMC
Madec, E., A. Laszkiewicz, A. Iwanicki, M. Obuchowski, and S. Seror. 2002. Characterization of a membrane-linked Ser/Thr protein kinase in Bacillus subtilis, implicated in developmental processes. Mol. Microbiol. 46:571-586. PubMed
Martin, B., P. Garcia, M. P. Castanie, B. Glise, and J. P. Claverys. 1995. The recA gene of Streptococcus pneumoniae is part of a competence-induced operon and controls an SOS regulon. Dev. Biol. Stand. 85:293-300. PubMed
Martin, B., M. Prudhomme, G. Alloing, C. Granadel, and J. P. Claverys. 2000. Cross-regulation of competence pheromone production and export in the early control of transformation in Streptococcus pneumoniae. Mol. Microbiol. 38:867-878. PubMed
Méjean, V., C. Salles, L. C. Bullions, M. J. Bessman, and J. P. Claverys. 1994. Characterization of the mutX gene of Streptococcus pneumoniae as a homologue of Escherichia coli mutT, and tentative definition of a catalytic domain of the dGTP pyrophosphohydrolases. Mol. Microbiol. 11:323-330. PubMed
Mengin-Lecreulx, D., and J. van Heijenoort. 1996. Characterization of the essential gene glmM encoding phosphoglucosamine mutase in Escherichia coli. J. Biol. Chem. 271:32-39. PubMed
Molle, V., L. Kremer, C. Girard-Blanc, G. S. Besra, A. J. Cozzone, and J. F. Prost. 2003. An FHA phosphoprotein recognition domain mediates protein EmbR phosphorylation by PknH, a Ser/Thr protein kinase from Mycobacterium tuberculosis. Biochemistry 42:15300-15309. PubMed
Morrison, D. A. 1997. Streptococcal competence for genetic transformation: regulation by peptide pheromones. Microb. Drug Resist. 3:27-37. PubMed
Morrison, D. A., S. A. Lacks, W. R. Guild, and J. M. Hageman. 1983. Isolation and characterization of three new classes of transformation-deficient mutants of Streptococcus pneumoniae that are defective in DNA transport and genetic recombination. J. Bacteriol. 156:281-290. PubMed PMC
Morrison, D. A., M. C. Trombe, M. K. Hayden, G. A. Waszak, and J. D. Chen. 1984. Isolation of transformation-deficient Streptococcus pneumoniae mutants defective in control of competence, using insertion-duplication mutagenesis with the erythromycin resistance determinant of pAMβ1. J. Bacteriol. 159:870-876. PubMed PMC
Mortier-Barrière, I., A. de Saizieu, J. P. Claverys, and B. Martin. 1998. Competence-specific induction of recA is required for full recombination proficiency during transformation in Streptococcus pneumoniae. Mol. Microbiol. 27:159-170. PubMed
Nádvorník, R., T. Vomastek, J. Janecek, Z. Technikova, and P. Branny. 1999. Pkg2, a novel transmembrane protein Ser/Thr kinase of Streptomyces granaticolor. J. Bacteriol. 181:15-23. PubMed PMC
Nariya, H., and S. Inouye. 2002. Activation of 6-phosphofructokinase via phosphorylation by Pkn4, a protein Ser/Thr kinase of Myxococcus xanthus. Mol. Microbiol. 46:1353-1366. PubMed
Nariya, H., and S. Inouye. 2005. Modulating factors for the Pkn4 kinase cascade in regulating 6-phosphofructokinase in Myxococcus xanthus. Mol. Microbiol. 56:1314-1328. PubMed
Neu, J. M., S. V. MacMillan, J. R. Nodwell, and G. D. Wright. 2002. StoPK-1, a serine/threonine protein kinase from the glycopeptide antibiotic producer Streptomyces toyocaensis NRRL 15009, affects oxidative stress response. Mol. Microbiol. 44:417-430. PubMed
Ng, W. L., K. M. Kazmierczak, and M. E. Winkler. 2004. Defective cell wall synthesis in Streptococcus pneumoniae R6 depleted for the essential PcsB putative murein hydrolase or the VicR (YycF) response regulator. Mol. Microbiol. 53:1161-1175. PubMed
Ng, W. L., G. T. Robertson, K. M. Kazmierczak, J. Zhao, R. Gilmour, and M. E. Winkler. 2003. Constitutive expression of PcsB suppresses the requirement for the essential VicR (YycF) response regulator in Streptococcus pneumoniae R6. Mol. Microbiol. 50:1647-1663. PubMed
Ng, W. L., H. C. Tsui, and M. E. Winkler. 2005. Regulation of the pspA virulence factor and essential pcsB murein biosynthetic genes by the phosphorylated VicR (YycF) response regulator in Streptococcus pneumoniae. J. Bacteriol. 187:7444-7459. PubMed PMC
Novak, R., J. S. Braun, E. Charpentier, and E. Tuomanen. 1998. Penicillin tolerance genes of Streptococcus pneumoniae: the ABC-type manganese permease complex Psa. Mol. Microbiol. 29:1285-1296. PubMed
Nováková, L., L. Saskova, P. Pallova, J. Janecek, J. Novotna, A. Ulrych, J. Echenique, M. C. Trombe, and P. Branny. 2005. Characterization of a eukaryotic type serine/threonine protein kinase and protein phosphatase of Streptococcus pneumoniae and identification of kinase substrates. FEBS J. 272:1243-1254. PubMed
Oggioni, M. R., C. Trappetti, A. Kadioglu, M. Cassone, F. Iannelli, S. Ricci, P. W. Andrew, and G. Pozzi. 2006. Switch from planktonic to sessile life: a major event in pneumococcal pathogenesis. Mol. Microbiol. 61:1196-1210. PubMed PMC
Pearce, B. J., A. M. Naughton, E. A. Campbell, and H. R. Masure. 1995. The rec locus, a competence-induced operon in Streptococcus pneumoniae. J. Bacteriol. 177:86-93. PubMed PMC
Pestova, E. V., L. S. Havarstein, and D. A. Morrison. 1996. Regulation of competence for genetic transformation in Streptococcus pneumoniae by an auto-induced peptide pheromone and a two-component regulatory system. Mol. Microbiol. 21:853-862. PubMed
Pestova, E. V., and D. A. Morrison. 1998. Isolation and characterization of three Streptococcus pneumoniae transformation-specific loci by use of a lacZ reporter insertion vector. J. Bacteriol. 180:2701-2710. PubMed PMC
Peterson, S., R. T. Cline, H. Tettelin, V. Sharov, and D. A. Morrison. 2000. Gene expression analysis of the Streptococcus pneumoniae competence regulons by use of DNA microarrays. J. Bacteriol. 182:6192-6202. PubMed PMC
Peterson, S. N., C. K. Sung, R. Cline, B. V. Desai, E. C. Snesrud, P. Luo, J. Walling, H. Li, M. Mintz, G. Tsegaye, P. C. Burr, Y. Do, S. Ahn, J. Gilbert, R. D. Fleischmann, and D. A. Morrison. 2004. Identification of competence pheromone responsive genes in Streptococcus pneumoniae by use of DNA microarrays. Mol. Microbiol. 51:1051-1070. PubMed
Pfaffl, M. W. 2001. A new mathematical model for relative quantification in real-time RT-PCR. Nucleic Acids Res. 29:e45. PubMed PMC
Proudfoot, M., E. Kuznetsova, G. Brown, N. N. Rao, M. Kitagawa, H. Mori, A. Savchenko, and A. F. Yakunin. 2004. General enzymatic screens identify three new nucleotidases in Escherichia coli. Biochemical characterization of SurE, YfbR, and YjjG. J. Biol. Chem. 279:54687-54694. PubMed
Rajagopal, L., A. Clancy, and C. E. Rubens. 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. 278:14429-14441. PubMed
Rajagopal, L., A. Vo, A. Silvestroni, and C. E. Rubens. 2006. Regulation of cytotoxin expression by converging eukaryotic-type and two-component signalling mechanisms in Streptococcus agalactiae. Mol. Microbiol. 62:941-957. PubMed PMC
Rajagopal, L., A. Vo, A. Silvestroni, and C. E. Rubens. 2005. Regulation of purine biosynthesis by a eukaryotic-type kinase in Streptococcus agalactiae. Mol. Microbiol. 56:1329-1346. PubMed PMC
Reinscheid, D. J., K. Ehlert, G. S. Chhatwal, and B. J. Eikmanns. 2003. Functional analysis of a PcsB-deficient mutant of group B streptococcus. FEMS Microbiol. Lett. 221:73-79. PubMed
Reinscheid, D. J., B. Gottschalk, A. Schubert, B. J. Eikmanns, and G. S. Chhatwal. 2001. Identification and molecular analysis of PcsB, a protein required for cell wall separation of group B streptococcus. J. Bacteriol. 183:1175-1183. PubMed PMC
Rimini, R., B. Jansson, G. Feger, T. C. Roberts, M. de Francesco, A. Gozzi, F. Faggioni, E. Domenici, D. M. Wallace, N. Frandsen, and A. Polissi. 2000. Global analysis of transcription kinetics during competence development in Streptococcus pneumoniae using high density DNA arrays. Mol. Microbiol. 36:1279-1292. PubMed
Ross, W., K. K. Gosink, J. Salomon, K. Igarashi, C. Zou, A. Ishihama, K. Severinov, and R. L. Gourse. 1993. A third recognition element in bacterial promoters: DNA binding by the alpha subunit of RNA polymerase. Science 262:1407-1413. PubMed
Saeed, A. I., V. Sharov, J. White, J. Li, W. Liang, N. Bhagabati, J. Braisted, M. Klapa, T. Currier, M. Thiagarajan, A. Sturn, M. Snuffin, A. Rezantsev, D. Popov, A. Ryltsov, E. Kostukovich, I. Borisovsky, Z. Liu, A. Vinsavich, V. Trush, and J. Quackenbush. 2003. TM4: a free, open-source system for microarray data management and analysis. BioTechniques 34:374-378. PubMed
Stock, A. M., V. L. Robinson, and P. N. Goudreau. 2000. Two-component signal transduction. Annu. Rev. Biochem. 69:183-215. PubMed
Switzer, R. L., R. J. Turner, and Y. Lu. 1999. Regulation of the Bacillus subtilis pyrimidine biosynthetic operon by transcriptional attenuation: control of gene expression by an mRNA-binding protein. Prog. Nucleic Acid Res. Mol. Biol. 62:329-367. PubMed
Throup, J. P., K. K. Koretke, A. P. Bryant, K. A. Ingraham, A. F. Chalker, Y. Ge, A. Marra, N. G. Wallis, J. R. Brown, D. J. Holmes, M. Rosenberg, and M. K. Burnham. 2000. A genomic analysis of two-component signal transduction in Streptococcus pneumoniae. Mol. Microbiol. 35:566-576. PubMed
Turner, R. J., Y. Lu, and R. L. Switzer. 1994. Regulation of the Bacillus subtilis pyrimidine biosynthetic (pyr) gene cluster by an autogenous transcriptional attenuation mechanism. J. Bacteriol. 176:3708-3722. PubMed PMC
Tusher, V. G., R. Tibshirani, and G. Chu. 2001. Significance analysis of microarrays applied to the ionizing radiation response. Proc. Natl. Acad. Sci. USA 98:5116-5121. PubMed PMC
Umeyama, T., P. C. Lee, and S. Horinouchi. 2002. Protein serine/threonine kinases in signal transduction for secondary metabolism and morphogenesis in Streptomyces. Appl. Microbiol. Biotechnol. 59:419-425. PubMed
Villarino, A., R. Duran, A. Wehenkel, P. Fernandez, P. England, P. Brodin, S. T. Cole, U. Zimny-Arndt, P. R. Jungblut, C. Cervenansky, and P. M. Alzari. 2005. Proteomic identification of M. tuberculosis protein kinase substrates: PknB recruits GarA, a FHA domain-containing protein, through activation loop-mediated interactions. J. Mol. Biol. 350:953-963. PubMed
Walburger, A., A. Koul, G. Ferrari, L. Nguyen, C. Prescianotto-Baschong, K. Huygen, B. Klebl, C. Thompson, G. Bacher, and J. Pieters. 2004. Protein kinase G from pathogenic mycobacteria promotes survival within macrophages. Science 304:1800-1804. PubMed
Wang, J., C. Li, H. Yang, A. Mushegian, and S. Jin. 1998. A novel serine/threonine protein kinase homologue of Pseudomonas aeruginosa is specifically inducible within the host infection site and is required for full virulence in neutropenic mice. J. Bacteriol. 180:6764-6768. PubMed PMC
Yeats, C., R. D. Finn, and A. Bateman. 2002. The PASTA domain: a beta-lactam-binding domain. Trends Biochem. Sci. 27:438. PubMed
LocZ is a new cell division protein involved in proper septum placement in Streptococcus pneumoniae
General and molecular microbiology and microbial genetics in the IM CAS
Identification of multiple substrates of the StkP Ser/Thr protein kinase in Streptococcus pneumoniae