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 °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 α-helix movement.
CITATION STYLE
DeLange, F., Klaassen, C. H. W., Wallace-Williams, S. E., Bovee-Geurtst, P. H. M., Liu, X. M., DeGrip, W. J., & Rothschild, K. J. (1998). Tyrosine structural changes detected during the photoactivation of rhodopsin. Journal of Biological Chemistry, 273(37), 23735–23739. https://doi.org/10.1074/jbc.273.37.23735
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