Role of Retinal Isomerizations and Rotations in the Photocycle of Bacteriorhodopsin

Amnon Albeck, Noga Friedman, Mordechai Sheves, Michael Ottolenghi

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26 Scopus citations


Artificial bacteriorhodopsin (bR) pigments based on synthetic retinal analogues with selectively blocked single and double bonds were prepared. It was shown that rotations around single bonds C12-C13 and C10-C11 and isomerizations of C11=C12 and C9=C10 are not required either for initiating the photocycle of all-trans-bR or for forming its M412 intermediate. The results are discussed in light of mechanisms for the primary event (based on the C13=C14 isomerization) involving a concerted double-bond and single-bond rotation around adjacent C,C bonds. Similarly, the photoreaction of the 13-cis isomer of bacteriorhodopsin does not require isomerization about the C11=C12 double bond or rotation around C12-C13. It is also shown that 13-cis ⇔ all-trans (light-dark adaptation) reaction of bacteriorhodopsin does not involve additional rotations or isomerizations involving the C9-C13 section of the molecule.

Original languageEnglish
Pages (from-to)4614-4618
Number of pages5
JournalJournal of the American Chemical Society
Issue number15
StatePublished - 1986
Externally publishedYes


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