Bacteriorhodopsin analog regenerated with 13-desmethyl-13-iodoretinal.
The retinal analog 13-desmethyl-13-iodoretinal (13-iodoretinal) was newly synthesized and incorporated into apomembranes to reconstitute bacteriorhodopsin analog 13-I-bR. The absorption maximum was 598 nm and 97% of the chromophore was an all-trans isomer in the dark- and light-adapted state. Upon flash illumination, 13-I-bR underwent a transient spectral change in which a shorter wavelength intermediate (lambda(max) = 426 nm) similar to the M species of the native bR developed. Also, 13-I-bR showed light-induced proton pumping with rates and extents comparable to those seen in the native bR. The ultraviolet circular dichroism (CD) spectrum originating from the aromatic groups was different from that of the native bR, indicating that the substituted bulky iodine atom strongly interacts with neighboring amino acids. A projection difference Fourier map showed the labeled iodine was in the vicinity of helix C. 13-I-bR is an advantageous specimen for kinetic investigations of light-induced structural changes associated with the proton pumping cycle by x-ray diffraction.
Hiraki
Kenji
K
Suntory Institute for Bioorganic Research, Wakayamadai, Shimamoto, Osaka 618-0024, Japan.
Hamanaka
Toshiaki
T
Zheng
Xiang-Guo
XG
Shinada
Teturo
T
Kim
Jong-Moon
JM
Yoshihara
Kazuo
K
Kito
Yuji
Y
D001436:Bacteriorhodopsins / Q000737:chemistry / Q000502:physiology* / Q000528:radiation effects*; D003198:Computer Simulation; D003624:Darkness; D006863:Hydrogen-Ion Concentration / Q000528:radiation effects; D008027:Light; D008954:Models, Biological; D010775:Photic Stimulation; D010777:Photochemistry / Q000379:methods; D010782:Photolysis / Q000528:radiation effects; D017494:Proton Pumps / Q000502:physiology / Q000528:radiation effects; D018717:Purple Membrane / Q000502:physiology* / Q000528:radiation effects; D012172:Retinaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry / Q000502:physiology* / Q000528:radiation effects; D014961:X-Ray Diffraction / Q000379:methods
D017494:Proton Pumps; D001436:Bacteriorhodopsins; D012172:Retinaldehyde