Fourier transform infrared evidence for proline structural changes during the bacteriorhodopsin photocycle.

AUTOR(ES)

Rothschild, K J

RESUMO

Structural changes involving bacteriohodopsin proline residues have been investigated by Fourier transform infrared difference spectroscopy. Bacteriohodopsin (bR)-producing Halobacteria halobium were grown on a stringent medium containing either ring-perdeuterated proline or 15N-labeled proline. Comparison of the difference spectra obtained from the photoreactions of these labeled bR samples with those for unlabeled bR has led to the assignment of peaks due to proline vibrations. [proline-N15]bR exhibited a 15-cm-1 isotopic downshift of peaks in the 1420- to 1440-cm-1 region of the bR----K and bR----M difference spectra as well as a similar downshift of peaks found in the absolute absorption spectrum of bR. In contrast, [proline-D7]bR did not cause shifts in this region of the difference spectra. These results indicate that one or more prolines undergo a structural rearrangement during the bR photocycle involving the Xaa-Pro C--N peptide bond. This change may be directly coupled to the light-induced isomerization of the retinal chromophore from all-trans-retinal to 13-cis-retinal.

Documentos Relacionados

• pH-induced structural changes in bacteriorhodopsin studied by Fourier transform infrared spectroscopy.
• Protein dynamics in the bacteriorhodopsin photocycle: submillisecond Fourier transform infrared spectra of the L, M, and N photointermediates.
• Surface-bound optical probes monitor protein translocation and surface potential changes during the bacteriorhodopsin photocycle.
• Reversible steps in the bacteriorhodopsin photocycle.
• Spectrally silent transitions in the bacteriorhodopsin photocycle.