Proteorhodopsins

Sensory rhodopsin (sR) and proteorhodopsin 4.12.1. Sensory rhodopsin Halobacteria contain a family of four retinal proteins, bR, halorhodopsin (hR), sensory rhodopsin I (sR I), and phobor-hodopsin (pR or sensory rhodopsin II, sR II), which carry two distinct functions through common photochemical reactions. In particular, bR... 

The CP MAS NMR spectroscopy has been also extensively used for studies of proteins containing retinylidene chromophore like proteorhodopsin or bacteriorhodopsin. Bacteriorhodopsin is a protein component of purple membrane of Halobacterium salinarium.71 7 This protein contains 248 amino acids residues, forming a 7-helix bundle and a retinal chromophore covalently bound to Lys-216 via a Schiff base linkage. It is a light-driven proton pump that translocates protons from the inside to the outside of the cell. After photoisomerization of retinal, the reaction cycle is described by several intermediate states (J, K, L, M, N, O). Between L and M intermediate states, a proton transfer takes place from the protonated Schiff base to the anionic Asp85 at the central part of the protein. In the M and/or N intermediate states, the global conformational changes of the protein backbone take place. 

Shi et al.71 have assigned the backbone and side-chain chemical shifts for 103 of 238 residues of proteorhodopsin using solid state NMR spectroscopy. Analysis of the chemical shifts has allowed determination of protonation states of several carboxylic acids as well as boundaries and distortions of trans-membrane a-helices and secondary structure elements in the loops. It has been shown that internal Asp227, making a part of the counterion, is ionised, while Glul42 located close to the extracellular surface is neutral. 

Other CP MAS studies of bacteriorhodopsin, proteorhodopsin as well as bathorhodopsin have been reported.75-7... 

Dynamic nuclear polarisation (DNP) enhanced 15N CP MAS NMR has been exploited by Mark-Jurkauskas et al.79 in the studies of intermediates of the bacteriorhodopsin photocycle. The data for L intermediate were similar to those found for 13-ds,15-anti retylidene chloride, while those for K intermediate were similar to those of acid blue bacteriorhodopsin in which the Schiff base counterion was neutralised (Table 3). The 15N chemical shifts observed have shown that for bacteriorhodopsin, the Schiff base in K intermediate state loses contact with its counterion and establishes a new one in L intermediate state. The proton energy stored at the beginning in the electrostatic modes has been transformed to torsional modes. The transfer of energy is facilitated by the reduction of bond order alternation in the polyene chain when the counterion interaction is initially broken and is driven by the attraction of the Schiff base to a new counterion. 3D CP MAS experiments of NCOCX, NCACX, CONCA and CAN(CO)CA types have been used in studies of proteorhodopsin.71... 

The results of 15N CP MAS NMR studies for lysine, tryptophan and methionine labelled green variant of proteorhodopsin were presented by Shastri et al.80... 

Wang, W. W., Sineshchekov, O. A., Spudich, E. N., and Spudich, J. L. (2003). Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin.J. Biol. Chem. 36, 33985-33991. Waterbury, J. B., and Valois, F. W. (1993). Resistance to co-ocuring phages enables marine Synecho-cocus communities to coexist with cyanophages abundant in seawater. Appl. Environ. Microbiol. 59,... 

Pfleger N, Lorch M, Woemer AC et al (2008) Characterisation of Schiff base and chromophore in green proteorhodopsin by solid-state NMR. J Biomol NMR 40 15-21... 

Hellmich UA, Pfleger N, Glaubitz C (2009) F-19-MAS NMR on proteorhodopsin enhanced protocol for site-specific labeling for general application to membrane proteins. Photochem Photobiol 85 535-539... 

Shi L, Lake EMR, Ahmed MAM et al (2009) Solid-state NMR study of proteorhodopsin in the lipid enviroirment secondary structure and dynamics. Biochim Biophys Acta... 

Yang J, Aslimovska L, Glaubitz C (2011) Molecular dynamics of proteorhodopsin in lipid bilayers by solid-state NMR. J Am Chem Soc 133 4874-4881... 

Well-separated spectra were recorded for C, N-proteorhodopsin (PR), which is also a retinal protein from marine bacterioplanktons, from 2D crystals mainly formed by PR hexamer in DOPC bilayer [251—253]. 

S. Shastri, J. Vonck, N. Pfleger, W. Haase, W. Kuehlbrandt, C. Glaubitz, Proteorhodopsin characterisation of 2D crystals by electron microscopy and sohd state NMR, Biochim. Biophys. Acta 1768 (2007) 3012-3019. 

M.E. Ward, L. Shi, E. Lake, S. Krishnamurthy, H. Hutchins, L.S. Brown, V. Ladizhansky, Proton-detected sohd-state NMR reveals intramembrane polar networks in a seven-hehcal transmembrane protein proteorhodopsin, J. Am. Chem. Soc. 133 (2011) 17434-17443. 

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