AUTHOR=Song Yingcai , Zhang Bing , Guo Fei , Yang Maojun , Li Yang , Liu Zhi-Qiang 

TITLE=Identification of Intracellular β-Barrel Residues Involved in Ion Selectivity in the Mechanosensitive Channel of Thermoanaerobacter tengcongensis

JOURNAL=Frontiers in Physiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2017.00832

DOI=10.3389/fphys.2017.00832

ISSN=1664-042X

ABSTRACT=<p>The mechanosensitive channel of small conductance (MscS) is a bacterial membrane pore that senses membrane tension and protects cells from lysis by releasing osmolytes. MscS is a homoheptameric channel with a cytoplasmic domain with seven portals and a β-barrel opening to the cytoplasm. <italic>Tt</italic>MscS, an MscS channel from <italic>Thermoanaerobacter tengcongensis</italic>, is an anion-selective channel. A previous study from our laboratory has defined the crucial role of β-barrel in the anion selectivity of <italic>Tt</italic>MscS (Zhang et al., <xref ref-type="bibr" rid="B35">2012</xref>). However, the mechanistic details by which the β-barrel determines anion selectivity remain unclear. Here, using mutagenesis and patch-clamp recordings, we investigated the function and structural correlations between β-barrels and the anion selectivity of <italic>Tt</italic>MscS at the atomic level. Our results indicated that mutation of V274, a residue at the center of the inner wall of the β-barrel in <italic>Tt</italic>MscS, caused the anion selectivity of <italic>Tt</italic>MscS reverse to cation selectivity. Moreover, the electrostatic potential (T272) and physical size (L276) of residues in the inner wall of β-barrel also determine the anion selectivity of <italic>Tt</italic>MscS. In summary, the present study confirmed that the β-barrel region of <italic>Tt</italic>MscS acts as a “selective filter” that renders <italic>Tt</italic>MscS anion selectivity.</p>