Identification of PamA as a PII-binding membrane protein important in nitrogen-related and sugar-catabolic gene expression in Synechocystis sp. PCC 6803.

The PII signaling protein plays a pivotal role in the coordination of carbon and nitrogen metabolism in a wide variety of bacteria, Archaea, and plant chloroplasts. By using a yeast two-hybrid screening system, we identified a transmembrane protein, designated PamA (encoded by sll0985), as a PII-binding protein in Synechocystis sp. PCC 6803. The interaction between PII and PamA was confirmed in vitro, and the interaction was inhibited in the presence of ATP and 2-oxoglutarate, whereas the interaction was not influenced by the phosphorylation status of PII. Northern blot analyses revealed that the transcripts of a set of nitrogen-related genes, including nblA, nrtABCD, and ureG, were decreased in a pamA deletion mutant. The mRNA and protein levels of a group 2 sigma factor SigE were also reduced by the pamA mutation, and transcripts for sugar catabolic genes, such as gap1, zwf, and gnd that are under the control of SigE, were consequently decreased in the pamA mutant. In addition, the pamA mutant was found to be unable to grow in glucose-containing media. These results indicate that PamA has a role in the transcript control of genes for nitrogen and sugar metabolism in Synechocystis sp. PCC 6803.