Participation of bacteriorhodopsin active-site lysine backbone in vibrations associated with retinal photochemistry.
Bacteriorhodopsin (bR) has been biosynthetically prepared with lysine deuterated at its alpha carbon (C alpha--H). The labeled membranes containing bR were investigated by difference Fourier transform infrared (FTIR) spectroscopy. It has been derived from K/bR and M/bR difference spectra (K and M are photocycle intermediates) that several bands previously assigned to the retinal chromophore are coupled to the C alpha--H. The vibrational modes that exhibit this coupling are principally associated with C15--H and N--H vibrations. [C alpha--2H]Lysine-labeled bR was fragmented enzymatically, and bR structures were regenerated with the C alpha--2H label either on lysine-216 and -172 or on the remaining five lysine residues of the protein. FTIR studies of the regenerated bR system, together with methylation of all lysines except the active-site lysine, reveal that the changes observed due to backbone labeling arise from the active-site lysine. The intensity of the C15--H out-of-plane wag is interpreted as a possible indication of a twist around the C15 = N bond.
Gat
Y
Y
Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel.
Grossjean
M
M
Pinevsky
I
I
Takei
H
H
Rothman
Z
Z
Sigrist
H
H
Lewis
A
A
Sheves
M
M
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003903:Deuterium; D008239:Lysine; D010777:Photochemistry; D011487:Protein Conformation; D012172:Retinaldehyde / Q000502:physiology*; D013055:Spectrophotometry, Infrared
D001436:Bacteriorhodopsins; D003903:Deuterium; D008239:Lysine; D012172:Retinaldehyde