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Query: UMLS:C1832526 (PCC)
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IS892, one of the several insertion sequence (IS) elements discovered in Anabaena sp. strain PCC 7120 (Y. Cai and C. P. Wolk, J. Bacteriol. 172:3138-3145, 1990), is 1,675 bp with 24-bp near-perfect inverted terminal repeats and has two open reading frames (ORFs) that could code for proteins of 233 and 137 amino acids. Upon insertion into target sites, this IS generates an 8-bp directly repeated target duplication. A 32-bp sequence in the region between ORF1 and ORF2 is similar to the sequence of the inverted termini. Similar inverted repeats are found within each of those three segments, and the sequences of these repeats bear some similarity to the 11-bp direct repeats flanking the 11-kb insertion interrupting the nifD gene of this strain (J. W. Golden, S. J. Robinson, and R. Haselkorn, Nature [London] 314:419-423, 1985). A sequence similar to that of a binding site for the Escherichia coli integration host factor is found about 120 bp from the left end of IS892. Partial nucleotide sequences of active IS elements IS892N and IS892T, members of the IS892 family from the same Anabaena strain, were shown to be very similar to the sequence of IS892.
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PMID:Characterization of insertion sequence IS892 and related elements from the cyanobacterium Anabaena sp. strain PCC 7120. 165 18

The genome of the cyanobacterium Synechococcus sp. strain PCC 7942 contains three psbA genes which encode two forms of the D1 protein of photosystem II. Experiments using psbA-lacZ translational fusions and Western blot (immunoblot) analysis have shown that the psbA genes respond differently to changes in light intensity, altering the ratio of the two forms of D1 in the thylakoid membrane. Each gene produces a 1.2-kilobase (kb) mRNA. A probe specific for psbAII transcripts also identified a 1.6-kb mRNA which starts 419 base pairs upstream of the 5' end of the 1.2-kb species and overlaps the entire 1.2-kb transcript. This 419-base-pair region includes an open reading frame (ORF1) of 114 amino acids. We investigated the effects of changes in light intensity on psbAII transcript levels in a series of light shift experiments in the wild-type Synechococcus sp. and in AMC084, a mutant which does not produce the 1.6-kb transcript. After exposure to high light intensities for 15 min, the level of the 1.2-kb psbAII transcript increased in both strains. This transcript was not detected in either strain after transfer to low light intensity. The psbAIII transcript showed the same pattern of response as the 1.2-kb psbAII transcript, whereas the 1.6-kb psbAII transcript was unaffected by different light intensities. The psbAI transcript levels responded oppositely to those of psbAII and psbAIII. These data, considered along with previous results obtained by using lacZ translational gene fusions, indicate that the response of psbA genes to changes in light intensity is controlled primarily at the transcriptional level.
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PMID:Different and rapid responses of four cyanobacterial psbA transcripts to changes in light intensity. 210 29

A part of the tRNA(Leu)(UAA) gene containing a 240-nucleotide group I intron was amplified by PCR from cyanobacterium Synechococcus PCC 6301 genomic DNA. The pre-tRNA synthesized from the cloned PCR product was efficiently self-spliced in vitro under physiological conditions. The gene encoding the tRNA(Leu)(UAA), trnL-UAA, was isolated from a Synechococcus PCC 6301 genomic library and the nucleotide sequence of a 2,167-bp portion was determined. The trnL-UAA consists of a 34-bp 5' exon, a 240-bp group I intron and a 50-bp 3' exon. In addition, three open reading frames (ORF1, ORF2 and ORF3) were found in the 5' and 3' flanking regions of trnL-UAA. The predicted protein sequence of ORF3, which is located 74-bp upstream from trnL-UAA on the opposite strand, shows 66.2% amino acid identity to that of the Synechocystis PCC 6803 gene encoding subunit L of NADH dehydrogenase (ndhL).
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PMID:Genes encoding the group I intron-containing tRNA(Leu) and subunit L of NADH dehydrogenase from the cyanobacterium Synechococcus PCC 6301. 758 50

The gene encoding ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) activase (rca) was uniformly localized downstream from the genes encoding the large and small subunits of RubisCO (rbcL and rbcS) in three strains of Anabaena species. However, two open reading frames (ORF1 and ORF2), situated between rbcS and rca in Anabaena sp. strain CA, were not found in the intergenic region of Anabaena variabilis and Anabaena sp. strain PCC 7120. During autotrophic growth of Anabaena cells, rca and rbc transcripts accumulated in the light and diminished in the dark; light-dependent expression of these genes was not affected by the nitrogen source and the concentration of exogenous CO2 supplied to the cells. When grown on fructose, rca- and rbc-specific transcripts accumulated in A. variabilis regardless of whether the cells were illuminated. Transcript levels, however, were much lower in dark-grown heterotrophic cultures than in photoheterotrophic cultures. In photoheterotrophic cultures, the expression of the rca and rbc genes was similar to that in cultures grown with CO2 as the sole source of carbon. Although the rbcL-rbcS and rca genes are linked and are in the same transcriptional orientation in Anabaena strains, hybridization of rbc and rca to distinct transcripts suggested that these genes are not cotranscribed, consistent with the results of primer extension and secondary structure analysis of the nucleotide sequence. Transcription from ORF1 and ORF2 was not detected under the conditions examined, and the function of these putative genes remains unknown.
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PMID:Transcription control of ribulose bisphosphate carboxylase/oxygenase activase and adjacent genes in Anabaena species. 796 23

Both strands of small plasmid pCB2.4 from the unicellular cyanobacterium Synechocystis PCC 6803 have been sequenced and analyzed. pCB2.4 contains 2345 bp and 57% A+T. Three open reading frames (ORFs) were identified in the nucleotide sequence of one strand of pCB2.4. ORF1 and ORF3 may encode basic proteins with calculated pI values of 7.71 and 9.96, respectively. The products of these ORFs have been compared to published protein sequences in databases and do not show significant homology to other proteins including replication proteins. pCB2.4 is not similar at the global DNA level to another 2.4-kbp plasmid, pCA2.4, present in the same cells, which has been found to replicate by a rolling-circle mechanism via a single-stranded intermediate. However, a short region (37 bp) is similar in pCA2.4 and pCB2.4. This region contains a potential nicking site (GATA) for replication proteins encoded by a group of plasmids that replicate by a rolling-circle mechanism and might be used as the origin of replication for these plasmids. Detection of a low level of single-stranded intermediate for pCB2.4 in the Synechocystis 6803 suggests that pCB2.4 may also replicate by a rolling-circle mechanism.
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PMID:The complete DNA sequence and replication analysis of the plasmid pCB2.4 from the cyanobacterium Synechocystis PCC 6803. 802 21

A gene (phoV) encoding an alkaline phosphatase from Synechococcus sp. strain PCC 7942 was isolated by screening a plasmid gene bank for expression of alkaline phosphatase activity in Escherichia coli JM103. Two independent clones carrying the same alkaline-phosphatase-encoding gene were isolated. One of these clones (pKW1) was further analysed and the nucleotide sequence of a contiguous 3234 bp DNA fragment was determined. Two complete open reading frames (ORF1 and phoV) and an incomplete ORF3 were identified reading in the same direction. The deduced phoV gene product showed 34% identity to the alkaline phosphatase PhoA from Zymomonas mobilis, and the N-terminal part of the putative ORF3 protein exhibited 57% identity to a protein of unknown function from Frankia sp. Insertional inactivation of the Synechococcus PCC 7942 phoV gene failed, indicating an essential role for either the phoV or the ORF3 gene product. PhoV consists of 550 amino acid residues, resulting in a molecular mass of 61.3 kDa. To overexpress the Synechococcus PCC 7942 phoV gene in E. coli, plasmid pKW1 was transformed into a phoA mutant of E. coli (CC118). In E. coli strain CC118(pKW1) PhoV was expressed constitutively with high rates of activity, and was shown to be membrane associated in the periplasmic space. After partial purification of the recombinant PhoV, it was shown that, like other alkaline phosphatases, the Synechococcus PhoV had a broad pH optimum in the alkaline region and a broad substrate specificity for phosphomonoesters, required Zn2+ for activity, and was inhibited by phosphate. In contrast to several other alkaline phosphatases, PhoV was inhibited by Mn2+. Due to the lack of a Synechococcus PCC 7942 phoV mutant strain, the function of PhoV remains uncertain. However, the present results show that Synechococcus PCC 7942 has a second, probably phosphate-irrepressible, alkaline phosphatase (PhoV, 61.3 kDa) in addition to the phosphate-repressible enzyme (PhoA, 145 kDa) already described.
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PMID:The cyanobacterium Synechococcus sp. strain PCC 7942 contains a second alkaline phosphatase encoded by phoV. 857 98