Importance of bound divalent cations to the tyrosine deprotonation during the photocycle of bacteriorhodopsin

AUTOR(ES)

Dupuis, Paul

RESUMO

The transient absorption changes occurring at 297 nm during the photocycles of the deionized and acidified bacteriorhodopsins (blue membranes) were studied. As opposed to what happens during the photocycle of the purple membrane, for the blue membranes only the fast absorption increase corresponding to trans-cis isomerization of the retinal chromophore is present; the slow rise attributed to the tyrosine deprotonation is not observed. The addition of different salts to the deionized membrane restores the original color and causes a tyrosine deprotonation during the photocycle. This suggests that the presence of cations is required for the deprotonation of tyrosine as it is for the deprotonation of the retinylidene Schiff base. These results are discussed in terms of the recently proposed cation model for the observed deprotonation processes in the photocycle of bacteriorhodopsin.

Documentos Relacionados

• On the molecular mechanisms of the Schiff base deprotonation during the bacteriorhodopsin photocycle
• Evidence for the involvement of more than one metal cation in the Schiff base deprotonation process during the photocycle of bacteriorhodopsin
• Surface-bound optical probes monitor protein translocation and surface potential changes during the bacteriorhodopsin photocycle.
• Chromophore motion during the bacteriorhodopsin photocycle: polarized absorption spectroscopy of bacteriorhodopsin and its M-state in bacteriorhodopsin crystals.
• Restriction of motion of protein side chains during the photocycle of bacteriorhodopsin.