AI Article Synopsis
- KR2 is a unique light-driven ion pump that can transport sodium or protons, but how it chooses which ion to transport is still a mystery.
- The researchers used advanced solid-state NMR techniques to study specific parts of KR2, identifying key residues and the effects of a specific mutation (H30A) that alters its ion selectivity towards sodium.
- Their findings suggest that the H30A mutation impacts the entire structure of KR2, influencing the retinal binding pocket and sodium binding sites, with support from time-resolved optical spectroscopy data.
Article Abstract
Krokinobacter eikastus rhodopsin 2 (KR2) is a pentameric, light-driven ion pump, which selectively transports sodium or protons. The mechanism of ion selectivity and transfer is unknown. By using conventional as well as dynamic nuclear polarization (DNP)-enhanced solid-state NMR, we were able to analyse the retinal polyene chain between positions C10 and C15 as well as the Schiff base nitrogen in the KR2 resting state. In addition, 50% of the KR2 C and N resonances could be assigned by multidimensional high-field solid-state NMR experiments. Assigned residues include part of the NDQ motif as well as sodium binding sites. Based on these data, the structural effects of the H30A mutation, which seems to shift the ion selectivity of KR2 primarily to Na, could be analysed. Our data show that it causes long-range effects within the retinal binding pocket and at the extracellular Na binding site, which can be explained by perturbations of interactions across the protomer interfaces within the KR2 complex. This study is complemented by data from time-resolved optical spectroscopy.
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| http://dx.doi.org/10.1016/j.jsb.2018.06.001 | DOI Listing |
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