title: Regulation of purine biosynthesis by a eukaryotic-type kinase in Streptococcus agalactiae.
abstract: Group B streptococci (GBS) are the principal causal agents of human neonatal pneumonia, sepsis and meningitis. We had previously described the existence of a eukaryotic-type serine/threonine kinase (Stk1) and phosphatase (Stp1) in GBS that regulate growth and virulence of the pathogen. Our previous results also demonstrated that these enzymes reversibly phosphorylated an inorganic pyrophosphatase. To understand the role of these eukaryotic-type enzymes on growth of GBS, we assessed the stk1-mutants for auxotrophic requirements. In this report, we describe that in the absence of the kinase (Stk1), GBS are attenuated for de novo purine biosynthesis and are consequently growth arrested. During growth in media lacking purines, the intracellular G nucleotide pools (GTP, GDP and GMP) are significantly reduced in the Stk1-deficient strains, while levels of A nucleotides (ATP, ADP and AMP) are marginally increased when compared with the isogenic wild-type strain. We provide evidence that the reduced pools of G nucleotides result from altered activity of the IMP utilizing enzymes, adenylosuccinate synthetase (PurA) and IMP dehydrogenase (GuaB) in these strains. We also demonstrate that Stk1 and Stp1 reversibly phosphorylate and consequently regulate PurA activity in GBS. Collectively, these data indicate the novel role of eukaryotic-type kinases in regulation of metabolic processes such as purine biosynthesis.
authors.affiliation: Division of Infectious Disease and Department of Pediatrics, Children's Hospital and Regional Medical Center and University of Washington, Suite 300, Mail Stop CW, 307 Westlake Ave. North, Seattle, WA 98109, USA. lakshmi.rajagopal@seattlechildrens.org
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Rajagopal
authors.forename: Anthony
authors.initials: A
authors.lastname: Vo
authors.forename: Aurelio
authors.initials: A
authors.lastname: Silvestroni
authors.forename: C E
authors.initials: CE
authors.lastname: Rubens
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000265:Adenylosuccinate Synthase / Q000378:metabolism; D005816:Genetic Complementation Test; D006153:Guanosine Diphosphate / Q000378:metabolism; D006157:Guanosine Monophosphate / Q000032:analysis; D006160:Guanosine Triphosphate / Q000378:metabolism; D007168:IMP Dehydrogenase / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D011687:Purines / Q000096:biosynthesis*; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D011687:Purines; D006153:Guanosine Diphosphate; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D006157:Guanosine Monophosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D007168:IMP Dehydrogenase; D010770:Phosphotransferases; D000265:Adenylosuccinate Synthase