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Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

The functional mechanism of the light-driven sodium pump Krokinobacter eikastus rhodopsin 2 (KR2) raises fundamental questions since the transfer of cations must differ from the better-known principles of rhodopsin-based proton pumps. Addressing these questions must involve a better understanding of...

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Detalles Bibliográficos
Autores principales: Jakdetchai, Orawan, Eberhardt, Peter, Asido, Marvin, Kaur, Jagdeep, Kriebel, Clara Nassrin, Mao, Jiafei, Leeder, Alexander J., Brown, Lynda J., Brown, Richard C. D., Becker-Baldus, Johanna, Bamann, Christian, Wachtveitl, Josef, Glaubitz, Clemens
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Association for the Advancement of Science 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7954446/
https://www.ncbi.nlm.nih.gov/pubmed/33712469
http://dx.doi.org/10.1126/sciadv.abf4213
Descripción
Sumario:The functional mechanism of the light-driven sodium pump Krokinobacter eikastus rhodopsin 2 (KR2) raises fundamental questions since the transfer of cations must differ from the better-known principles of rhodopsin-based proton pumps. Addressing these questions must involve a better understanding of its photointermediates. Here, dynamic nuclear polarization–enhanced solid-state nuclear magnetic resonance spectroscopy on cryo-trapped photointermediates shows that the K-state with 13-cis retinal directly interconverts into the subsequent L-state with distinct retinal carbon chemical shift differences and an increased out-of-plane twist around the C14-C15 bond. The retinal converts back into an all-trans conformation in the O-intermediate, which is the key state for sodium transport. However, retinal carbon and Schiff base nitrogen chemical shifts differ from those observed in the KR2 dark state all-trans conformation, indicating a perturbation through the nearby bound sodium ion. Our findings are supplemented by optical and infrared spectroscopy and are discussed in the context of known three-dimensional structures.