Evidence for a perturbation of arginine-82 in the bacteriorhodopsin photocycle from time-resolved infrared spectra.

M difference spectrum are attributable to guanidino group vibrations of R82, based on their shift upon isotope substitution of the thioethylguanidinium attached to R82C and on their disappearance in the R82A spectrum. The frequencies and intensities of these IR bands support the NMR-based conclusion that there is a significant perturbation of R82 during the bR photocycle. However, the unusually low frequencies attributable to R82 guandino group vibrations in M, approximately 1640 and approximately 1545 cm(-)(1), would require a reexamination of a previously discarded hypothesis, namely, that the perturbation of R82 involves a change in its ionization state. -->
Grant Information: GM08323 United States GM NIGMS NIH HHS; GM34548 United States GM NIGMS NIH HHS; GM46854 United States GM NIGMS NIH HHS
Substance Nomenclature: 0 (Carboxylic Acids)
0 (Protons)
53026-44-1 (Bacteriorhodopsins)
94ZLA3W45F (Arginine)
OF5P57N2ZX (Alanine)
Entry Date(s): Date Created: 20001029 Date Completed: 20001130 Latest Revision: 20190613
Update Code: 20231215
DOI: 10.1021/bi000426q
PMID: 11052671
Autor: Hutson MS; Chemistry Department, Syracuse University, Syracuse, New York 13244-4100, USA., Alexiev U, Shilov SV, Wise KJ, Braiman MS
Jazyk: angličtina
Zdroj: Biochemistry [Biochemistry] 2000 Oct 31; Vol. 39 (43), pp. 13189-200.
DOI: 10.1021/bi000426q
Abstrakt: Arginine-82 (R82) of bacteriorhodopsin (bR) has long been recognized as an important residue due to its absolute conservation in the archaeal rhodopsins and the effects of R82 mutations on the photocycle and proton release. However, the nature of interactions between R82 and other residues of the protein has remained difficult to decipher. Recent NMR studies showed that the two terminal nitrogens of R82 experience a highly perturbed asymmetric environment during the M state trapped at cryogenic temperatures [Petkova et al. (1999) Biochemistry 38, 1562-1572]. Although previous low-temperature FT-IR spectra of wild-type and mutant bR samples have demonstrated effects of R82 on vibrations of other amino acid side chains, no bands in these spectra were assignable to vibrations of R82 itself. We have now measured time-resolved FT-IR difference spectra of bR intermediates in the wild-type and R82A proteins, as well as in samples of the R82C mutant with and without thioethylguanidinium attached via a disulfide linkage at the unique cysteine site. Several bands in the bR --> M difference spectrum are attributable to guanidino group vibrations of R82, based on their shift upon isotope substitution of the thioethylguanidinium attached to R82C and on their disappearance in the R82A spectrum. The frequencies and intensities of these IR bands support the NMR-based conclusion that there is a significant perturbation of R82 during the bR photocycle. However, the unusually low frequencies attributable to R82 guandino group vibrations in M, approximately 1640 and approximately 1545 cm(-)(1), would require a reexamination of a previously discarded hypothesis, namely, that the perturbation of R82 involves a change in its ionization state.
Databáze: MEDLINE
Externí odkaz: