Reisomerization of retinal represents a molecular switch mediating Na+ uptake and release by a bacterial sodium-pumping rhodopsin.
J Biol Chem
; 298(9): 102366, 2022 09.
Article
em En
| MEDLINE
| ID: mdl-35963435
ABSTRACT
Sodium-pumping rhodopsins (NaRs) are membrane transporters that utilize light energy to pump Na+ across the cellular membrane. Within the NaRs, the retinal Schiff base chromophore absorbs light, and a photochemically induced transient state, referred to as the "O intermediate", performs both the uptake and release of Na+. However, the structure of the O intermediate remains unclear. Here, we used time-resolved cryo-Raman spectroscopy under preresonance conditions to study the structure of the retinal chromophore in the O intermediate of an NaR from the bacterium Indibacter alkaliphilus. We observed two O intermediates, termed O1 and O2, having distinct chromophore structures. We show O1 displays a distorted 13-cis chromophore, while O2 contains a distorted all-trans structure. This finding indicated that the uptake and release of Na+ are achieved not by a single O intermediate but by two sequential O intermediates that are toggled via isomerization of the retinal chromophore. These results provide crucial structural insight into the unidirectional Na+ transport mediated by the chromophore-binding pocket of NaRs.
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MEDLINE
Assunto principal:
Sódio
/
Bacteriorodopsinas
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Bacteroidetes
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2022
Tipo de documento:
Article