title: Negative and positive temperature dependence of potassium leak in MscS mutants: Implications for understanding thermosensitive channels.
abstract: Bacterial mechanosensitive channel of small conductance (MscS) is a protein, whose activity is modulated by membrane tension, voltage and cytoplasmic crowding. MscS is a homoheptamer and each monomer consists of three transmembrane helices (TM1-3). Hydrophobic pore of the channel is made of TM3s surrounded by peripheral TM1/2s. MscS gating is a complex process, which involves opening and inactivation in response to the increase of membrane tension. A number of MscS mutants were isolated. Among them mutants affecting gating have been found including gain-of-function (GOF) and loss-of-function (LOF) that open at lower or at higher thresholds, respectively. Previously, using an in vivo screen we isolated multiple MscS mutants that leak potassium and some of them were GOF or LOF. Here we show that for a subset of these mutants K+ leak is negatively (NTD) or positively (PTD) temperature dependent. We show that temperature reliance of these mutants does not depend on how MS gating is affected by a particular mutation. Instead, we argue that NTD or PTD leak is due to the opposite allosteric coupling of the structures that determine the temperature dependence to the channel gate. In PTD mutants an increased hydration of the pore vestibule is directly coupled to the increase in the channel conductance. In NTD mutants, at higher temperatures an increased hydration of peripheral structures leads to complete separation of TM3 and a pore collapse.
authors.affiliation: Department of Cell Biology, The Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland. Electronic address: p.koprowski@nencki.gov.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Koprowski
authors.affiliation: Department of Cell Biology, The Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
authors.forename: Malgorzata A
authors.initials: MA
authors.lastname: Sliwinska
authors.affiliation: Department of Cell Biology, The Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Kubalski
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005838:Genotype; D057927:Hydrophobic and Hydrophilic Interactions; D015640:Ion Channel Gating; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D008958:Models, Molecular; D009154:Mutation; D010641:Phenotype; D011188:Potassium / Q000378:metabolism*; D011312:Pressure; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013696:Temperature; D013697:Thermosensing; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; D007473:Ion Channels; C469542:MscS protein, E coli; D011188:Potassium
keywords: Bacteria; Channel; Mechanosensitive; Potassium; Thermosensitive