The icfG gene cluster of Synechocystis sp. strain PCC 6803 encodes an Rsb/Spo-like protein kinase, protein phosphatase, and two phosphoproteins.
A set of open reading frames (ORFs) potentially encoding signal transduction proteins are clustered around icfG, a gene implicated in the regulation of carbon metabolism, in the genome of Synechocystis sp. strain PCC 6803. slr1860 is the ORF for icfG, whose predicted product resembles the protein phosphatases SpoIIE, RsbU, and RsbX from Bacillus subtilis. Bracketing slr1860/icfG are (i) ORF slr1861, whose predicted product resembles the SpoIIAB, RsbT, and RsbW protein kinases from B. subtilis, and (ii) ORFs slr1856 and slr1859, whose predicted products resemble the respective phosphoprotein substrates for the B. subtilis protein kinases: SpoIIAA, RsbS, and RsbV. In order to determine whether the protein products encoded by these ORFs possessed the functional capabilities suggested by sequence comparisons, each was expressed in Escherichia coli as a histidine-tagged fusion protein and analyzed for its ability to participate in protein phosphorylation-dephosphorylation processes in vitro. It was observed that ORF slr1861 encoded an ATP-dependent protein kinase capable of phosphorylating Slr1856 and, albeit with noticeably lower efficiency, Slr1859. Site-directed mutagenesis suggests that Slr1861 phosphorylated these proteins on Ser-54 and Ser-57, respectively. Slr1860 exhibited divalent metal ion-dependent protein-serine phosphatase activity. It catalyzed the dephosphorylation of Slr1856, but not Slr1859, in vitro.
Shi
L
L
Department of Biochemistry and the Institute for Genomics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0308, USA.
Bischoff
K M
KM
Kennelly
P J
PJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics*; D017931:DNA Primers; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D016680:Genome, Bacterial; D006868:Hydrolysis; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames / Q000235:genetics; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine; D012808:Sigma Factor; D015398:Signal Transduction / Q000502:physiology; D013379:Substrate Specificity; D014157:Transcription Factors
D001426:Bacterial Proteins; D017931:DNA Primers; D010750:Phosphoproteins; D012808:Sigma Factor; C120822:Slr1856 protein, Synechocystis; C120821:Slr1859 protein, Synechocystis; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus; D008345:Manganese; D012694:Serine; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C120823:Slr1861 protein, Synechocystis; C120820:ICFG protein, Synechocystis; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases; C091162:RsbU protein, Bacillus subtilis; D008274:Magnesium