title: [Characterization of the Rela/SpoT homologue slr1325 (syn-rsh) of the cyanobacterium Synechocystis sp. PCC6803].
abstract: OBJECTIVE
  Nucleotide guanosine-3', 5'-(bis) pyrophosphate (ppGpp) synthesized by (ppGpp) synthesase RelA or bifunctional ppGpp synthase/degradase RelA/SpoT, mediates bacterial stringent response to various stressful conditions. Here we characterized the slr1325 (syn-rsh) gene encoding a RelA/SpoT homolog (Syn-RSH) of the cyanobacterium Synechocystis sp. PCC6803.
  
  
  METHODS
  We performed phenotypic complement test using Escherichia coli strain with(p) ppGpp-synthesis defect to determine Syn-RSH function(s), and employed chromatographic analysis of 32P-labeled cellular mononucleotides to detect the accumulation of ppGpp in Escherichia coli strains expressing Syn-RSH and in Synechocystis sp. PCC6803.
  
  
  RESULTS
  Syn-RSH expression in E. coli relA/spoT double mutant was able to restore the cell growth arrest; Chromatographic analysis of 32P-labeled cellular mononucleotides revealed that Syn-RSH expression resulted in the synthesis of ppGpp in E. coli strain with relA and spoT mutant mutation. Additionally, Synechocystis cells accumulated a low level of ppGpp under laboratory growth conditions.
  
  
  CONCLUSIONS
  Syn-RSH possesses ppGpp synthase/degradase activities, and ppGpp is required for Synechocystis cell viability under normal growth conditions.
authors: College of Environment, Jiangsu University, Zhenjiang 212013, China. xgmiao_2009@163.com
authors: Xiaogang
authors: X
authors: Miao
authors: Huiling
authors: H
authors: Liu
authors: Degang
authors: D
authors: Ning
mesh_terms: D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D006159:Guanosine Tetraphosphate / Q000096:biosynthesis; D008025:Ligases / Q000235:genetics*; D046939:Synechocystis / Q000235:genetics*
chemical_list: D006159:Guanosine Tetraphosphate; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases