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    Bacterial rhodopsin: evidence for a new type of phototrophy in the sea (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-09-16
    Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beja, O -- Aravind, L -- Koonin, E V -- Suzuki, M T -- Hadd, A -- Nguyen, L P -- Jovanovich, S B -- Gates, C M -- Feldman, R A -- Spudich, J L -- Spudich, E N -- DeLong, E F -- HG01775-02S1/HG/NHGRI NIH HHS/ -- R01GM27750/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2000 Sep 15;289(5486):1902-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039-0628, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10988064" target="_blank"〉PubMed〈/a〉
    Keywords: Aerobiosis ; Amino Acid Sequence ; Archaea/classification/physiology ; Bacteria/genetics ; *Bacterial Physiological Phenomena ; Cloning, Molecular ; Escherichia coli ; Gammaproteobacteria/classification/genetics/*physiology ; Molecular Sequence Data ; Oceans and Seas ; Photochemistry ; Photosynthesis ; Phylogeny ; Phytoplankton/genetics/physiology ; Protein Binding ; Proton Pumps/physiology ; Retinaldehyde/metabolism ; Rhodopsin/*physiology ; Rhodopsins, Microbial ; *Water Microbiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Structural conservation of an ancient tRNA sensor in eukaryotic glutaminyl-tRNA synthetase (2012)
    Oxford University Press
    Details
    Publication Date: 2012-04-24
    Description: In all organisms, aminoacyl tRNA synthetases covalently attach amino acids to their cognate tRNAs. Many eukaryotic tRNA synthetases have acquired appended domains, whose origin, structure and function are poorly understood. The N-terminal appended domain (NTD) of glutaminyl-tRNA synthetase (GlnRS) is intriguing since GlnRS is primarily a eukaryotic enzyme, whereas in other kingdoms Gln-tRNA Gln is primarily synthesized by first forming Glu-tRNA Gln , followed by conversion to Gln-tRNA Gln by a tRNA-dependent amidotransferase. We report a functional and structural analysis of the NTD of Saccharomyces cerevisiae GlnRS, Gln4. Yeast mutants lacking the NTD exhibit growth defects, and Gln4 lacking the NTD has reduced complementarity for tRNA Gln and glutamine. The 187-amino acid Gln4 NTD, crystallized and solved at 2.3 Å resolution, consists of two subdomains, each exhibiting an extraordinary structural resemblance to adjacent tRNA specificity-determining domains in the GatB subunit of the GatCAB amidotransferase, which forms Gln-tRNA Gln . These subdomains are connected by an apparent hinge comprised of conserved residues. Mutation of these amino acids produces Gln4 variants with reduced affinity for tRNA Gln , consistent with a hinge-closing mechanism proposed for GatB recognition of tRNA. Our results suggest a possible origin and function of the NTD that would link the phylogenetically diverse mechanisms of Gln-tRNA Gln synthesis.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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