Abstract
Bacterial mechanosensitive channels are evolved to protect cells against hypo-osmotic shock. In Escherichia coli, the general mechanism of mechanosensing has been characterized by extensive studies on one of the six small conductance channels, MscS. However, it remains unclear how other homologs function. Here, we describe the structure of YnaI, one of the MscS homologs, in its non-conducting state at 3.27A resolution determined by cryo electron microscopy. The structure reveals the complete sensor paddle domains, which is the first time for any MscS-like channels. In the pockets between sensor paddles, there are ordered lipid densities, implying the functional importance of the protein-lipid interactions. Together with previously published mutagenesis as well as comparison with MscS structures, the results shed lights on the organization of the paddles, the ion-conducting pathway as well as the heptameric assembly in YnaI.
Published Version
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