Spectral properties of bacteriophytochrome AM1_5894 in the chlorophyll d-containing cyanobacterium Acaryochloris marina.

ABSTRACT: Acaryochloris marina, a unicellular oxygenic photosynthetic cyanobacterium, has uniquely adapted to far-red light-enriched environments using red-shifted chlorophyll d. To understand red-light use in Acaryochloris, the genome of this cyanobacterium was searched for red/far-red light photoreceptors from the phytochrome family, resulting in identification of a putative bacteriophytochrome AM1_5894. AM1_5894 contains three standard domains of photosensory components as well as a putative C-terminal signal transduction component consisting of a histidine kinase and receiver domain. The photosensory domains of AM1_5894 autocatalytically assemble with biliverdin in a covalent fashion. This assembled AM1_5894 shows the typical photoreversible conversion of bacterial phytochromes with a ground-state red-light absorbing (Pr) form with ?BV max[Pr] 705?nm, and a red-light inducible far-red light absorbing (Pfr) form with ?BV max[Pfr] 758?nm. Surprisingly, AM1_5894 also autocatalytically assembles with phycocyanobilin, involving photoreversible conversion of ?PCB max[Pr] 682?nm and ?PCB max[Pfr] 734?nm, respectively. Our results suggest phycocyanobilin is also covalently bound to AM1_5894, while mutation of a cysteine residue (Cys11Ser) abolishes this covalent binding. The physiological function of AM1_5894 in cyanobacteria containing red-shifted chlorophylls is discussed.

SUBMITTER: Loughlin PC 

PROVIDER: S-EPMC4901347 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature