Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dissociation constant (K(d)) was determined for the binding of the transcriptional regulator NtcA to a number of NtcA-activated promoters of the cyanobacterium Synechococcus sp. PCC 7942, as well as to mutant versions of those promoters altered in their NtcA-binding sites. K(d) values obtained ranged from 27 nM for the NtcA-binding site in the glnA promoter to ca. 1.4 microM for the site in the glnB promoter. Changes in the sequence signature of NtcA-binding sites (i.e. GTAN(8)TAC) either completely prevented binding of NtcA or drastically decreased its affinity for the promoter revealing that the GTN(10)AC subset is essential for binding. The importance of the flanking A/T-rich sequences and of a conserved CA dimer found in between the GTA/TAC triplets was also stressed. Thus, this structure seems to be optimal for the binding of NtcA. Comparison of K(d) values for NtcA binding to native promoters showed that differences in the sequence of their NtcA binding sites determine extensive differences in the affinity of the regulator for those sites.
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PMID:Analysis of binding sites for the nitrogen-control transcription factor NtcA in the promoters of Synechococcus nitrogen-regulated genes. 1239 92

Two herbicide-resistant strains of the cyanobacterium Synechococcus sp. PCC 7002 are compared to the wild-type with respect to the DNA changes which result in herbicide resstance. The mutations have previously been mapped to a region of the cyanobacterial genome which encodes oneof three copies of psbA, the gene which encodes the 32 kDa Qb-binding protein also known as D1 (Buzby et al. 1987). The DNA sequence of the wild-type gene was first determined and used as a comparison to that of the mutant alleles. A point mutation at codon 211 in the psbA1 coding locus (TTC) to TCC) results in an amino acid change from phenylalanine to serine in the D1 protein. This mutation confers resistance to atrazine and diuron at seven times and at two times the minimal inhibitory concentration (MIC) for the wild-type, respectively. A mutation at codon 211 resulting in herbicide resistance has not previously been described in the literature. A second point mutation at codon 219 in the psbA1 coding locus (GTA to ATA) results in an amino acid change from valine to isoleucine in the D1 protein. This mutation confers resistance to diuron and atrazine at ten times and at two times the MIC for the wild-type, respectively. An identical codon change conferring similar herbicide resistance patterns has previously been described in Chlamydomonas reinhardtii. The atrazine-resistance phenotype in Synechococcus sp. PCC 7002 was shown to be dominant by plasmid segregation analysis.
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PMID:Genetic analysis of two new mutations resulting in herbicide resistance in the cyanobacterium Synechcoccus sp. PCC 7002. 2443 Sep 93