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Synthesis and Properties of Bacteriorhodopsin Analogs Containing Electron-Density Labels in the Chromophore Moiety

E. V. Mironova1, A. Yu. Lukin1, S. V. Shevyakov1, S. G. Alexeeva1, V. I. Shvets1, O. V. Demina2, A. A. Khodonov1*, and L. V. Khitrina3

1Lomonosov State Academy of Fine Chemical Technology, pr. Vernadskogo 86, Moscow, 117571 Russia; fax: (095) 434-8233; E-mail: biotechnology@mtu-net.ru

2Emanuel Institute for Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 117977 Russia; E-mail: chembio@sky.chph.ras.ru

3Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899 Russia, fax: (095) 939-3181; E-mail: khitr@phtbio.genebee.msu.su

* To whom correspondence should be addressed.

Received April 4, 2001; Revision received June 13, 2001
A method for synthesis of retinal analogs labeled with electron-density groups is suggested. The interaction of these polyene compounds with bacterioopsin in apomembrane of Halobacterium salinarum was tested. A retinal analog containing a crown-ether receptor group is able to interact readily with bacterioopsin giving rise to rapid formation of a pigment with absorption maximum at 460 nm. This pigment is capable of undergoing cyclic photoconversion. The crown-bacteriorhodopsin photocycle is extremely slow and its quantum efficiency is very low (~3% of that in native bacteriorhodopsin). This photocycle includes an M-like intermediate with a differential absorption maximum at 380 nm. A retinal analog in which the beta-ionone ring is replaced by ferrocene moiety forms a stable chromoprotein with the main absorption band at 483 nm and a shoulder near 590-610 nm.
KEY WORDS: bacteriorhodopsin, bacterioopsin, chromophore, apomembranes, photocycle, M-intermediate, electron-density labels, retinal, bacteriorhodopsin analogs, synthesis and photochemical properties, crown ether, ferrocene