IDENTIFICATION OF A 2ND PSAC GENE IN THE CYANOBACTERIUM SYNECHOCYSTIS SP PCC6803

The psaC gene encodes the 9 kDa protein subunit of photosystem I that carries the iron-sulfur centers F(A) and F(B). The paper describes the sequence and transcription analysis of a second psaC gene (psaC2) from Synechocystis sp. PCC6803. The psaC2 gene is transcribed into an abundant monocistronic mRNA. The deduced amino acid sequence of PSI-C2 is very similar to the protein sequences from two other cyanobacteria (Synechococcus sp. PCC7002 and Nostoc sp. PCC8009). In contrast, the recently isolated psaC1 gene is not transcribed and the PSI-C1 amino acid sequence shows the highest similarity to the proteins from higher plants.