Analysis of a novel flavin-binding sensor-type PAS domain in cyanobacterium Synechocystis sp. PCC 6803

Abstract

PAS domain superfamily, which binds flavin, is known as sensors of blue light or redox changes. The FAD-binding PAS domain of Aer protein is known as redox sensor in Escherichia coli to regulate aerotaxis. We found in the cyanobacterial genomes that one of the PAS domains of Slr1759 protein is significantly homologous to the FAD-binding domain of Aer. Slr1759 protein is a multidomain protein which contains two PAS, GAF, His kinase and response regulator domains. We overexpressed the segment containing the PAS domain as His-tagged fusion protein in E. coli. The purified protein showed absorption spectrum typical for the oxidized flavin but quite distinct from that of Aer. We will discuss possible role of the flavin-binding PAS domain together with the disruption phenotype in Synechocystis.