Tyrosine structural changes detected during the photoactivation of rhodopsin.
We present the first Fourier transform infrared (FTIR) analysis of an isotope-labeled eukaryotic membrane protein. A combination of isotope labeling and FTIR difference spectroscopy was used to investigate the possible involvement of tyrosines in the photoactivation of rhodopsin (Rho). Rho --> MII difference spectra were obtained at 10 degrees C for unlabeled recombinant Rho and isotope-labeled L-[ring-2H4]Tyr-Rho expressed in Spodoptera frugiperda cells grown on a stringent culture medium containing enriched L-[ring-2H4]Tyr and isolated using a His6 tag. A comparison of these difference spectra revealed reproducible changes in bands that correspond to tyrosine and tyrosinate vibrational modes. A similar pattern of tyrosine/tyrosinate bands has also been observed in the bR --> M transition in bacteriorhodopsin, although the sign of the bands is reversed. In bacteriorhodopsin, these bands were assigned to Tyr-185, which along with Pro-186 in the F-helix, may form a hinge that facilitates alpha-helix movement.
DeLange
F
F
Department of Biochemistry, Institute of Cellular Signalling, University of Nijmegen, 6500 HB, Nijmegen, The Netherlands.
Klaassen
C H
CH
Wallace-Williams
S E
SE
Bovee-Geurts
P H
PH
Liu
X M
XM
DeGrip
W J
WJ
Rothschild
K J
KJ
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003903:Deuterium; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000528:radiation effects; D012243:Rhodopsin / Q000096:biosynthesis / Q000737:chemistry* / Q000528:radiation effects*; D017550:Spectroscopy, Fourier Transform Infrared; D018411:Spodoptera; D014162:Transfection; D014443:Tyrosine
D011994:Recombinant Proteins; D014443:Tyrosine; D012243:Rhodopsin; D003903:Deuterium