Microsecond atomic force sensing of protein conformational dynamics: Implications for the primary light-induced events in bacteriorhodopsin

Itay Rousso, Edward Khachatryan, Yahaloma Gat, Igor Brodsky, Michael Ottolenghi, Mordechai Sheves, Aaron Lewis

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

In this paper a new atomic force sensing technique is presented for dynamically probing conformational changes in proteins. The method is applied to the light-induced changes in the membrane-bound proton pump bacteriorhodopsin (bR). The microsecond time-resolution of the method, as presently implemented, covers many of the intermediates of the bR photocycle which is well characterized by spectroscopical methods. In addition to the native pigment, we have studied bR proteins substituted with chemically modified retinal chromophores. These synthetic chromophores were designed to restrict their ability to isomerize, while maintaining the basic characteristic of a large light-induced charge redistribution in the vertically excited Franck-Condon state. An analysis of the atomic force sensing signals lead us to conclude that protein conformational changes in bR can be initiated as a result of a light-triggered redistribution of electronic charge in the retinal chromophore, even when isomerization cannot take place. Although the coupling mechanism of such changes to the light- induced proton pump is still not established, our data question the current working hypothesis which attributes all primary events in retinal proteins to an initial trans mutually implies cis isomerization.

Original languageEnglish
Pages (from-to)7937-7941
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume94
Issue number15
DOIs
StatePublished - 22 Jul 1997
Externally publishedYes

ASJC Scopus subject areas

  • General

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