Analysis of transcriptional regulation mediated by a cAMP receptor protein in the filamentous cyanobacterium Anabaena sp. PCC 7120

Abstract

Two open reading frames, alr0295 and alr2325, were found to encode the cAMP receptor proteins (CRPs) in the genome of the filamentous cyanobacterium Anabaena sp. PCC 7120. These open reading frames were named ancrpA and ancrpB, respectively, and those translated products were showed cAMP- and DNA-binding affinity. Since cAMP-binding affinity of AnCrpA is higher than that of AnCrpB, cAMP signaling in Anabaena sp. PCC 7120 is thought to be mediated mainly by AnCrpA. Therefore, the target genes for AnCrpA were identified using a DNA microarray method. The results showed that the transcription of some nitrogen fixation-related genes were repressed in the ancrpA disruptant. Electrophoretic mobility shift assay revealed that AnCrpA bound to the 5' upstream regions of target genes. It is concluded that AnCrpA regulates the expression of the nitrogen fixation-related genes.