| Structural highlights
Function
BACR1_HALWD Light-driven proton pump. The chromophore contains 78% all-trans- and 22% 13-cis-retinal in the dark and 90% all-trans- and 10% 13-cis-retinal upon illumination with >500 nm light.[1] [2] [3]
Publication Abstract from PubMed
Retinal bound light-driven proton pumps are widespread in eukaryotic and prokaryotic organisms. Among these pumps, bacteriorhodopsin (BR) proteins cooperate with ATP synthase to convert captured solar energy into a biologically consumable form, ATP. In an acidic environment or when pumped-out protons accumulate in the extracellular region, the maximum absorbance of BR proteins shifts markedly to the longer wavelengths. These conditions affect the light-driven proton pumping functional exertion as well. In this study, wild-type crystal structure of a BR with optical stability under wide pH range from a square halophilic archaeon, Haloquadratum walsbyi (HwBR), was solved in two crystal forms. One crystal form, refined to 1.85 A resolution, contains a trimer in the asymmetric unit, whereas another contains an antiparallel dimer was refined at 2.58 A. HwBR could not be classified into any existing subgroup of archaeal BR proteins based on the protein sequence phylogenetic tree, and it showed unique absorption spectral stability when exposed to low pH values. All structures showed a unique hydrogen-bonding network between Arg(82) and Thr(201), linking the BC and FG loops to shield the retinal-binding pocket in the interior from the extracellular environment. This result was supported by R82E mutation that attenuated the optical stability. The negatively charged cytoplasmic side and the Arg(82)-Thr(201) hydrogen bond may play an important role in the proton translocation trend in HwBR under acidic conditions. Our findings have unveiled a strategy adopted by BR proteins to solidify their defenses against unfavorable environments and maintain their optical properties associated with proton pumping.
Structural and Functional Studies of a Newly Grouped Haloquadratum walsbyi Bacteriorhodopsin Reveal the Acid-resistant Light-driven Proton Pumping Activity.,Hsu MF, Fu HY, Cai CJ, Yi HP, Yang CS, Wang AH J Biol Chem. 2015 Dec 4;290(49):29567-77. doi: 10.1074/jbc.M115.685065. Epub 2015, Oct 19. PMID:26483542[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Sudo Y, Ihara K, Kobayashi S, Suzuki D, Irieda H, Kikukawa T, Kandori H, Homma M. A microbial rhodopsin with a unique retinal composition shows both sensory rhodopsin II and bacteriorhodopsin-like properties. J Biol Chem. 2011 Feb 25;286(8):5967-76. doi: 10.1074/jbc.M110.190058. Epub 2010 , Dec 6. PMID:21135094 doi:http://dx.doi.org/10.1074/jbc.M110.190058
- ↑ Lobasso S, Lopalco P, Vitale R, Saponetti MS, Capitanio G, Mangini V, Milano F, Trotta M, Corcelli A. The light-activated proton pump Bop I of the archaeon Haloquadratum walsbyi. Photochem Photobiol. 2012 May-Jun;88(3):690-700. doi:, 10.1111/j.1751-1097.2012.01089.x. Epub 2012 Feb 9. PMID:22248212 doi:http://dx.doi.org/10.1111/j.1751-1097.2012.01089.x
- ↑ Sudo Y, Okazaki A, Ono H, Yagasaki J, Sugo S, Kamiya M, Reissig L, Inoue K, Ihara K, Kandori H, Takagi S, Hayashi S. A blue-shifted light-driven proton pump for neural silencing. J Biol Chem. 2013 Jul 12;288(28):20624-32. doi: 10.1074/jbc.M113.475533. Epub, 2013 May 28. PMID:23720753 doi:http://dx.doi.org/10.1074/jbc.M113.475533
- ↑ Hsu MF, Fu HY, Cai CJ, Yi HP, Yang CS, Wang AH. Structural and Functional Studies of a Newly Grouped Haloquadratum walsbyi Bacteriorhodopsin Reveal the Acid-resistant Light-driven Proton Pumping Activity. J Biol Chem. 2015 Dec 4;290(49):29567-77. doi: 10.1074/jbc.M115.685065. Epub 2015, Oct 19. PMID:26483542 doi:http://dx.doi.org/10.1074/jbc.M115.685065
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