In vivo activity of the nitrogen control transcription factor NtcA is subjected to metabolic regulation in Synechococcus sp. strain PCC 7942.

The cyanobacterial protein NtcA is a global transcriptional regulator of genes involved in nitrogen assimilation that are subjected to ammonium-promoted repression and is itself controlled by positive autoregulation. Strain CSI70 derived from Synechococcus sp. strain PCC 7942 was constructed to overexpress an additional ntcA gene copy from a constitutive promoter.

Complement component C7 deficiency in a Spanish family.

Different genetic mutations have been described in complement component C7 deficiency, a molecular defect which is clinically associated with an increased susceptibility to neisserial recurrent infections, although some cases remain asymptomatic. In this work we report the genetic bases of C7 deficiency in one Spanish family. Exon-specific PCR and sequencing revealed a novel point mutation at nucleotide 615 (exon 6) leading to a stop codon (UGG to UGA) in the patient, his mother, and sister.

Carbon supply and 2-oxoglutarate effects on expression of nitrate reductase and nitrogen-regulated genes in Synechococcus sp. strain PCC 7942.

Synthesis of nitrate reductase in the unicellular cyanobacterium Synechococcus sp. strain PCC 7942 took place at a slow rate when the cells were incubated without a supply of inorganic carbon, but addition to these cells of CO(2)/bicarbonate or, in a Synechococcus strain transformed with a gene encoding a 2-oxoglutarate permease, 2-oxoglutarate stimulated expression of the enzyme. Induction by 2-oxoglutarate was also observed at the mRNA level for two nitrogen-regulated genes, nir and amt1, but not for the photosystem II D1 protein-encoding gene psbA1.

Analysis of binding sites for the nitrogen-control transcription factor NtcA in the promoters of Synechococcus nitrogen-regulated genes.

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.

The NtcA-activated amt1 gene encodes a permease required for uptake of low concentrations of ammonium in the cyanobacterium Synechococcus sp. PCC 7942.

In the unicellular cyanobacterium Synechococcus sp. PCC 7942, ammonium/methylammonium transport activity has been characterized but ammonium transport genes have not been described. The amt1 gene encoding a permease responsible for high-affinity [14C]methylammonium transport in Synechococcus sp.