Spectral properties of bacteriophytochrome AM1_5894 in the chlorophyll d-containing cyanobacterium Acaryochloris marina.
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 λBV max[Pr] 705 nm, and a red-light inducible far-red light absorbing (Pfr) form with λBV max[Pfr] 758 nm. Surprisingly, AM1_5894 also autocatalytically assembles with phycocyanobilin, involving photoreversible conversion of λPCB max[Pr] 682 nm and λPCB 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.
School of Biological Sciences, University of Sydney, NSW 2006, Australia.
Patrick C
PC
Loughlin
School of Biological Sciences, University of Sydney, NSW 2006, Australia.
Zane
Z
Duxbury
School of Biological Sciences, University of Sydney, NSW 2006, Australia.
Tendo T Mukasa
TT
Mugerwa
School of Biological Sciences, University of Sydney, NSW 2006, Australia.
Penelope M C
PM
Smith
Department of Chemistry and Biomolecular Sciences, Macquarie University, NSW 2109, Australia.
Robert D
RD
Willows
School of Biological Sciences, University of Sydney, NSW 2006, Australia.
Min
M
Chen
D002734:Chlorophyll / Q000737:chemistry / Q000235:genetics*; D000458:Cyanobacteria / Q000737:chemistry / Q000235:genetics*; D003545:Cysteine / Q000737:chemistry / Q000235:genetics; D016680:Genome, Bacterial / Q000235:genetics; D000071677:Histidine Kinase / Q000235:genetics / Q000378:metabolism; D008027:Light; D020283:Photoreceptors, Microbial / Q000235:genetics; D010788:Photosynthesis / Q000235:genetics* / Q000528:radiation effects; D010834:Phytochrome / Q000737:chemistry / Q000235:genetics*; D015398:Signal Transduction / Q000528:radiation effects
D020283:Photoreceptors, Microbial; D010834:Phytochrome; D002734:Chlorophyll; C107509:chlorophyll d; D000071677:Histidine Kinase; D003545:Cysteine