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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Eukaryotic-like protein Ser/Thr and Tyr kinases have only recently been discovered in prokaryotes. In most cases, their biochemical properties have been poorly characterized. The nitrogen-fixing and heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 houses a family of eukaryotic-like Ser/Thr kinases. Some of these enzymes are required for cell growth or development under certain conditions. None of them, however, has been shown experimentally to possess Ser/Thr kinase activity. A gene, pknC, encoding a novel putative Ser/Thr kinase was isolated from Anabaena sp. PCC 7120. The recombinant PknC was shown to be phosphorylated on a Thr residue. This phosphorylation was probably due to the autophosphorylation activity of PknC itself because mutation of two amino acid residues within the subdomain II of its catalytic domain eliminated the phosphorylation of PknC. PknC displayed also a Ser kinase activity towards several nonspecific substrates, and the two residues needed for PknC autophosphorylation was equally required for the phosphorylation of other substrates. PknC is thus a Ser/Thr kinase with broad substrate specificity. The activity of PknC is likely to be regulated in vivo in order to limit the spectrum of its substrate specificity.
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PMID:Characterization of PknC, a Ser/Thr kinase with broad substrate specificity from the cyanobacterium Anabaena sp. strain PCC 7120. 1124 8

The family of Ser/Thr and/or Tyr kinases and that of His kinases play essential roles in signal transduction. For a long time, the former has been found in eukaryotes, the latter in prokaryotes. Studies in the last decade have shown, however, that most bacteria possess from one to more than 10 genes encoding Ser/Thr kinases. This observation raises an important question concerning the evolutionary origin of Ser/Thr kinases found in bacteria. To answer this question, we have analyzed a family of 11 genes encoding Ser/Thr kinases in the cyanobacterium Synechocystis sp. PCC 6803. This bacterium contains the largest number of Ser/Thr kinases among all bacteria whose genomic sequences have been released so far. In this study, we have developed a user-friendly computer program for statistical analysis of codon usages and GC content. The results demonstrate that Ser/Thr kinases have similar codon usages and GC contents as the average of all possible open reading frames (ORFs) deduced from the genome. In contrast, ORFs encoding transposases, as a control in our analysis, display a disparity in both codon usage and GC content, confirming their multiple origin and genetic promiscuity. In light of our results, we propose that Ser/Thr kinases existed before the divergence between prokaryotes and eukaryotes during evolution, or were laterally transferred into prokaryotes at the early stages of bacterial evolution. If Ser/Thr kinases have persisted ever since in prokaryotes under evolutionary pressure, it is then expected that they play important, possibly even essential roles in regulating bacterial activities as do their counterparts in eukaryotes.
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PMID:On the origin of Ser/Thr kinases in a prokaryote. 1141 Mar 53

Two novel cyclic depsipeptides were isolated from axenic cultures of the terrestrial cyanobacterium Scytonema hofmanni PCC 7110 and designated scyptolin A and B. Amino acid analyses in context with mass and 1H/13C NMR spectroscopies revealed a composition typical for heterologous cyanopeptolins but containing the uncommon residue 3'-chloro-N-methyl-Tyr (cmTyr) and a unique sidechain. Scyptolin A and B both consist of the N-acylated peptide But(1)-Ala(2)-Thr(3)-Thr(4)-Leu(5)-Ahp(6) (3-amino-6-hydroxy-2-oxo-1-piperidine)-Thr(7)-cmTyr(8)-Val(9), which forms a 19-membered ring by esterification of the carboxyl of Val(9) with the hydroxyl of Thr(4). In scyptolin B, the hydroxyl of the Thr(3) residue is additionally esterified with N-butyroyl-Ala. Both scyptolin A and B exhibit selective inhibition of porcine pancreatic elastase in vitro with IC(50) values of 3.1 microg/ml.
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PMID:Scyptolin A and B, cyclic depsipeptides from axenic cultures of Scytonema hofmanni PCC 7110. 1173 Aug 73

Two distinct families of protein kinases are involved in signal transduction: Ser, Thr and Tyr kinases, which are predominantly found among eukaryotes, and His kinases, as part of bacterial two-component signalling systems. Genetic studies in Arabidopsis and Saccharomyces have demonstrated that bacterial-type two-component systems may act upstream of Ser/Thr kinases in the same signalling pathway, but how this coupling is accomplished remains unclear. In the present study, we report the characterization of a protein kinase, HstK, from the N(2)-fixing cyanobacterium Anabaena sp. PCC 7120, that possesses both a Ser/Thr kinase domain and a His kinase domain. Proteins with a structural architecture similar to that of HstK can be found in the eukaryote, Schizosaccharomyces pombe, and the bacterium, Rhodococcus sp. M5. HstK was present in cells grown with NH(4)(+) or N(2) as the nitrogen source, but was absent in cells grown with NO(3)(-). The hstK gene was inactivated and the mutant phenotype was characterized. The catalytic domain of the Ser/Thr kinase of HstK functionally replaced that of Hog1p, a well-characterized protein kinase required for the response to high osmolarity in the S. cerevisiae heterologous system. The unusual multidomain structure of HstK suggests that a two-component system could be directly coupled to Ser/Thr kinases in the same signal transduction pathway.
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PMID:HstK, a cyanobacterial protein with both a serine/threonine kinase domain and a histidine kinase domain: implication for the mechanism of signal transduction. 1173 54

Computational analysis of gene structures in the genome of Anabaena sp. PCC 7120 revealed the presence of a large number of genes encoding proteins with multiple functional domains. This was most evident in the genes for signal transduction pathway and the related systems. Comparison of the putative amino acid sequences of the gene products with those in the Pfam database indicated that and PAS domains which may be involved in signal recognition were extremely abundant in Anabaena: 87 GAF domains in 62 ORFs and 140 PAS domains in 59 ORFs. As for the two-component signal transduction system, 73, 53, and 77 genes for simple sensory His kinases, hybrid His kinases and simple response regulators, respectively, many of which contained additional domains of diverse functions, were presumptively assigned. A total of 52 ORFs encoding putative Hanks-type Ser/Thr protein kinases with various domains such as WD-repeat, GAF and His kinase domains, as well as genes for presumptive protein phosphatases, were also identified. In addition, genes for putative transcription factors and for proteins in the cAMP signal transduction system harbored complex gene structures with multiple domains.
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PMID:Characterization of genes encoding multi-domain proteins in the genome of the filamentous nitrogen-fixing Cyanobacterium anabaena sp. strain PCC 7120. 1185 27

Recombinant plant-type asparaginases from the cyanobacteria Synechocystis sp. PCC (Pasteur culture collection) 6803 and Anabaena sp. PCC 7120, from Escherichia coli and from the plant Arabidopsis thaliana were expressed in E. coli with either an N-terminal or a C-terminal His tag, and purified. Although each of the four enzymes is encoded by a single gene, their mature forms consist of two protein subunits that are generated by autoproteolytic cleavage of the primary translation products at the Gly-Thr bond within the sequence GTI/VG. The enzymes not only deamidated asparagine but also hydrolysed a range of isoaspartyl dipeptides. As various isoaspartyl peptides are known to arise from proteolytic degradation of post-translationally altered proteins containing isoaspartyl residues, and from depolymerization of the cyanobacterial reserve polymer multi-L-arginyl-poly-L-aspartic acid (cyanophycin), plant-type asparaginases may not only function in asparagine catabolism but also in the final steps of protein and cyanophycin degradation. The properties of these enzymes are compared with those of the sequence-related glycosylasparaginases.
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PMID:Isoaspartyl dipeptidase activity of plant-type asparaginases. 1198 85

Propionic acidemia (PA) is an autosomal recessive inborn error in the catabolism of methionine, isoleucine, threonine, and valine, odd-numbered chain length fatty acids and cholesterol. Clinical symptoms are very heterogeneous and present as a severe neonatal-onset or a late-onset form. It is caused by a deficiency of propionyl-CoA carboxylase (PCC, EC 6.4.1.3), a biotin-dependent enzyme that catalyzes the carboxylation of propionyl-CoA to D-methylmalonyl-CoA. PCC is a heteropolymeric enzyme composed of alpha- and beta-subunits. A greater heterogeneity is observed in the PCCA gene, while for the PCCB gene, a limited number of mutations is responsible for the majority of the alleles characterized in both Caucasian and Oriental populations. We identified eight Korean patients with PA by organic acid analysis confirmed in five patients by the PCC enzyme assay in the lymphoblasts. Two neonatal-onset patients showed undetectable PCC activities while three cases with residual enzyme activities had relatively late manifestations. In the molecular analysis, we identified five novel mutations, Y439C, 1527del3, 1357insT, IVS12-8T-->A, and 31del10, and one known mutation, T428I in PCCB gene. Alleleic frequency of T428I in Korean patients with PA was 56.3% in this study. Two neonatal-onset patients with null enzyme activities were homozygotes with 1527del3 and T428I, respectively. This finding implies that T428I and 1527del3 mutation could be responsible for their severe clinical courses and null enzyme activities. The mRNA of PCCB gene in T428I and 1527del3 homozygotes were normal but in Western blot analysis, the betaPCC-subunit was only absent in 1527del3 homozygote patient suggesting different molecular pathology.
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PMID:Molecular analysis of PCCB gene in Korean patients with propionic acidemia. 1240 68

Anabaena sp. PCC 7120 is a cyanobacterium capable of performing several important biological functions: photosynthesis, nitrogen fixation, cell differentiation, cell-cell communication, etc. These activities require an extensive signaling capability in order to respond to the changing environment. Based on the genomic data, we have retrieved several gene families encoding signaling components. It is estimated that 211 genes encode two-component signaling elements, and 66 genes encode Ser/Thr kinases and phosphatases. These genes together represent 4.2% of the coding capacity of the whole genome, making Anabaena PCC 7120 a leading member among prokaryotes in terms of its signaling potential. It is known that two-component systems are composed of a few basic modules that can arrange into different structures best adapted for each signaling system. Many proteins in Anabaena PCC 7120 have incorporated both modules of two-component systems and catalytic domains of either Ser/Thr kinases or phosphatases. A family of 13 genes encode proteins with both a Ser/Thr kinase domain and a His kinase domain, and another four genes were also found whose products have both a response regulator domain and a Ser/Thr phosphatase domain. Of all the signaling proteins in Anabaena PCC 7120, about one third (35%) are conserved in the genome of the unicellular cyanobacterium strain Synechocystis sp. PCC 6803. Interestingly, one subfamily of His kinases and two subfamilies of response regulators are found in Anabaena PCC 7120 but are absent in Synechocystis PCC 6803. This study constitutes a basis for analyses of signal transduction in Anabaena PCC 7120 using functional genomic approaches.
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PMID:Genomic analysis of protein kinases, protein phosphatases and two-component regulatory systems of the cyanobacterium Anabaena sp. strain PCC 7120. 1248 98

In cyanobacteria, the isiA gene is required for cell adaptation to oxidative damage caused by the absence of iron. We show here that a putative Ser/Thr kinase gene, pkn22 (alr2052), is activated by iron deficiency and oxidative damage in Anabaena sp. PCC 7120. A pkn22 insertion mutant is unable to grow when iron is limiting. pkn22 regulates the expression of isiA (encoding CP43'), but not of isiB (encoding flavodoxin) and psbC (CP43). Fluorescence measurement at 77 K reveals the absence of the typical signature of CP43' associated with photosystem I in the mutant under iron-limiting conditions. We propose that Pkn22 is required for the function of isiA/CP43' and constitutes a regulatory element necessary for stress response.
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PMID:pkn22 (alr2502) encoding a putative Ser/Thr kinase in the cyanobacterium Anabaena sp. PCC 7120 is induced by both iron starvation and oxidative stress and regulates the expression of isiA. 1455 May 69

P700, the primary electron donor of photosystem I is an asymmetric dimer made of one molecule of chlorophyll a' (P(A)) and one of chlorophyll a (P(B)). While the carbonyl groups of P(A) are involved in hydrogen-bonding interactions with several surrounding amino acid side chains and a water molecule, P(B) does not engage in hydrogen bonding with the protein. Light-induced FTIR difference spectroscopy of the photooxidation of P700 has been combined with site-directed mutagenesis in Synechocystis sp. PCC 6803 to investigate the influence of these hydrogen bonds on the structure of P700 and P700(+). When the residue Thr A739, which donates a hydrogen bond to the 9-keto C=O group of P(A), is changed to Phe, a differential signal at 1653(+)/1638(-) cm(-1) in the P700(+)/P700 FTIR difference spectrum upshifts by approximately 30-40 cm(-1), as expected for the rupture of the hydrogen bond or, at least, a strong decrease of its strength. The same upshift is also observed in the FTIR spectrum of a triple mutant in which the residues involved in the three main hydrogen bonds to the 9-keto and 10a-carbomethoxy groups of P(A) have been changed to the symmetry-related side chains present around P(B). In addition, the spectrum of the triple mutant shows a decrease of a differential signal around 1735 cm(-1) and the appearance of a new signal around 1760 cm(-1). This is consistent with the perturbation of a bound 10a-ester C=O group that becomes free in the triple mutant. All of these observations support the assignment scheme proposed previously for the carbonyls of P700 and P700(+) [Breton, J., Nabedryk, E., and Leibl, W. (1999) Biochemistry 38, 11585-11592] and therefore reinforce our previous conclusions that the positive charge in P700(+) is largely delocalized over P(A) and P(B).
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PMID:FTIR spectroscopy of synechocystis 6803 mutants affected on the hydrogen bonds to the carbonyl groups of the PsaA chlorophyll of P700 supports an extensive delocalization of the charge in P700+. 1522 50


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