Chromophore Distortions in Photointermediates of Proteorhodopsin visualized by DNP-enhanced solid-state NMR.
 

Chromophore Distortions in Photointermediates of Proteorhodopsin visualized by DNP-enhanced solid-state NMR.

Chromophore Distortions in Photointermediates of Proteorhodopsin visualized by DNP-enhanced solid-state NMR.

J Am Chem Soc. 2017 Oct 13;:

Authors: Mehler M, Eckert CE, Leeder AJ, Kaur J, Fischer T, Kubatova N, Brown LJ, Brown RCD, Becker-Baldus J, Wachtveitl J, Glaubitz C

Abstract
Proteorhodopsin (PR) is the most abundant retinal protein on earth and functions as a light-driven proton pump. Despite of extensive efforts, structural data for PR photointermediate states have not been obtained. Based on DNP-enhanced solid-state NMR, we were able to analyze the retinal polyene chain between positions C10 and C15 as well as the Schiff base nitrogen in the ground state in comparison to light induced, cryo-trapped K- and M-states. A high M-state population could be achieved by preventing reprotonation of the Schiff base through a mutation of the primary proton donor (E108Q). Our data reveal unexpected large and alternating 13C chemical shift changes in the K-state propagating away from the Schiff base along the polyene chain. Furthermore, two different M-states have been observed reflecting the Schiff base reorientation after the de-protonation step. Our study provides novel insight into the photocycle of PR and also demonstrates the power of DNP-enhanced solid-state NMR to bridge the gap between functional and structural data and models.


PMID: 29027800 [PubMed - as supplied by publisher]



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