Interaction of tryptophan-182 with the retinal 9-methyl group in the L intermediate of bacteriorhodopsin.
An intense indole N-H stretching vibrational band at 3486 cm-1 in the difference Fourier transform infrared spectrum is one of the characteristic features of the L intermediate of bacteriorhodopsin [Maeda, Sasaki, Ohkita, Simpson, & Herzfeld (1992) Biochemistry 31, 12543]. This band is now assigned to tryptophan-182. The Trp182-->Phe (W182F) protein shows specific features in the difference spectrum in the visible region upon L formation, and exhibits great delay in the L-M conversion. Fourier transform infrared difference spectra further indicate that while the intensity of the C-methyl in-plane bending vibration at 1009 cm-1 is lost in the L intermediate of the wild type, its intensity remains high in the W182F protein. The intensity of the N-H stretching vibration upon L formation is diminished considerably in an artificial bacteriorhodopsin containing 9-desmethylretinal. It also exhibits delayed M formation. These results suggest that Trp182 interacts with the retinal side chain through the 9-methyl group, and thereby affects the L-to-M conversion.
Yamazaki
Y
Y
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Sasaki
J
J
Hatanaka
M
M
Kandori
H
H
Maeda
A
A
Needleman
R
R
Shinada
T
T
Yoshihara
K
K
Brown
L S
LS
Lanyi
J K
JK
D001436:Bacteriorhodopsins / Q000235:genetics / Q000378:metabolism*; D006217:Halobacterium; D008745:Methylation; D009154:Mutation; D011522:Protons; D012172:Retinaldehyde / Q000378:metabolism*; D012545:Schiff Bases; D017550:Spectroscopy, Fourier Transform Infrared; D014364:Tryptophan / Q000378:metabolism*
D011522:Protons; D012545:Schiff Bases; D001436:Bacteriorhodopsins; D014364:Tryptophan; D012172:Retinaldehyde