title: Bacterial rhodopsin: evidence for a new type of phototrophy in the sea.
abstract: Extremely halophilic archaea contain retinal-binding integral membrane proteins called bacteriorhodopsins that function as light-driven proton pumps. So far, bacteriorhodopsins capable of generating a chemiosmotic membrane potential in response to light have been demonstrated only in halophilic archaea. We describe here a type of rhodopsin derived from bacteria that was discovered through genomic analyses of naturally occuring marine bacterioplankton. The bacterial rhodopsin was encoded in the genome of an uncultivated gamma-proteobacterium and shared highest amino acid sequence similarity with archaeal rhodopsins. The protein was functionally expressed in Escherichia coli and bound retinal to form an active, light-driven proton pump. The new rhodopsin exhibited a photochemical reaction cycle with intermediates and kinetics characteristic of archaeal proton-pumping rhodopsins. Our results demonstrate that archaeal-like rhodopsins are broadly distributed among different taxa, including members of the domain Bacteria. Our data also indicate that a previously unsuspected mode of bacterially mediated light-driven energy generation may commonly occur in oceanic surface waters worldwide.
authors.affiliation: Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039-0628, USA.
authors.forename: O
authors.initials: O
authors.lastname: Béjà
authors.forename: L
authors.initials: L
authors.lastname: Aravind
authors.forename: E V
authors.initials: EV
authors.lastname: Koonin
authors.forename: M T
authors.initials: MT
authors.lastname: Suzuki
authors.forename: A
authors.initials: A
authors.lastname: Hadd
authors.forename: L P
authors.initials: LP
authors.lastname: Nguyen
authors.forename: S B
authors.initials: SB
authors.lastname: Jovanovich
authors.forename: C M
authors.initials: CM
authors.lastname: Gates
authors.forename: R A
authors.initials: RA
authors.lastname: Feldman
authors.forename: J L
authors.initials: JL
authors.lastname: Spudich
authors.forename: E N
authors.initials: EN
authors.lastname: Spudich
authors.forename: E F
authors.initials: EF
authors.lastname: DeLong
mesh_terms: D000332:Aerobiosis; D000595:Amino Acid Sequence; D001105:Archaea / Q000145:classification / Q000502:physiology; D001419:Bacteria / Q000235:genetics; D018407:Bacterial Physiological Phenomena; D003001:Cloning, Molecular; D004926:Escherichia coli; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009792:Oceans and Seas; D010777:Photochemistry; D010788:Photosynthesis; D010802:Phylogeny; D010839:Phytoplankton / Q000235:genetics / Q000502:physiology; D011485:Protein Binding; D017494:Proton Pumps / Q000502:physiology; D012172:Retinaldehyde / Q000378:metabolism; D012243:Rhodopsin / Q000502:physiology*; D025604:Rhodopsins, Microbial; D014871:Water Microbiology
chemical_list: D017494:Proton Pumps; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D012243:Rhodopsin; D012172:Retinaldehyde