Biochemical Analysis Of COS (Alr2428) Protein Of The N₂-fixing Cyanobacterium Anabaena sp. PCC 7120

Abstract

An oxygen sensor may play an important role in Anabaena sp. PCC 7120. FixL of rhizobia and DOS of Escherichia coli have a heme PAS domain as an oxygen sensor. In our latest study, a homologous heme PAS domain of COS (Alr2428) in Anabaena 7120 showed oxygen-responsive nature in vitro. Additionally, this protein contains histidine kinase domain at the C-terminal side of the heme PAS domain and response regulator and DNA-binding domains at the very N-terminus. Here, we prepared a recombinant protein with heme PAS and histidine kinase domains and analyzed the self-phosphorylation activity in the reduced or oxidized form. Next, we prepared another recombinant protein with response regulator and DNA-binding domains and analyzed the DNA-binding activity in the presence or absence of the acetyl phosphate. From these, possible oxygen-sensing mechanism of this protein will be discussed.