Blount, P. & Moe, P.C. Bacterial mechanosensitive channels: integrating physiology, structure and function. Trends Microbiol. 7, 420−424

Dept of Physiology, University of Texas Southwestern Medical Centre, Dallas, TX 75235-9040, USA.
Trends in Microbiology (Impact Factor: 9.19). 11/1999; 7(10):420-4. DOI: 10.1016/S0966-842X(99)01594-2
Source: PubMed


When confronted with hypo-osmotic stress, many bacterial species are able rapidly to adapt to the increase in cell turgor pressure by jettisoning cytoplasmic solutes into the medium through membrane-tension-gated channels. Physiological studies have confirmed the importance of these channels in osmoregulation. Mutagenesis of one of these channels, combined with structural information derived from X-ray crystallography, has given the first clues of how a mechanosensitive channel senses and responds to membrane tension.

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Available from: Paul Blount, Dec 23, 2013
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    • "Further details of the MscS gating mechanism are reviewed extensively elsewhere [17] [18]. Simulation studies have now extended this idea to other bacterial mechanosensitive channels (e.g., the pentameric MscL) [19] and are supported by a range of experimental observations such as the clustering of (hydrophilic) gain-of-function mutations onto the pore-lining face of the M1 helix [20] [21], as well as a direct correlation between residue hydrophilicity and channel function at Gly22 in TM1 [22]. Furthermore, recent subunit titration experiments have demonstrated that dynamically altering the hydrophilicity of a single subunit (by sulfhydryl modification of G22C) is sufficient to open the channel to allow the passage of ions and small molecules (up to ~ 10 Å in diameter). "
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    ABSTRACT: Biological ion channels are nanoscale transmembrane pores. When water and ions are enclosed within the narrow confines of a sub-nanometer hydrophobic pore, they exhibit behavior not evident from macroscopic descriptions. At this nanoscopic level, the unfavorable interaction between the lining of a hydrophobic pore and water may lead to stochastic liquid-vapor transitions. These transient vapor states are 'dewetted' i.e. effectively devoid of water molecules within all, or part of the pore, thus leading to an energetic barrier to ion conduction. This process, termed 'hydrophobic gating', was first observed in molecular dynamics simulations of model nanopores, where the principles underlying hydrophobic gating (i.e. changes in diameter, polarity, or transmembrane voltage) have now been extensively validated. Computational, structural and functional studies now indicate that biological ion channels may also exploit hydrophobic gating to regulate ion flow within their pores. Here we review the evidence for this process, and propose that this unusual behavior of water represents an increasingly important element in understanding the relationship between ion channel structure and function.
    Full-text · Article · Aug 2014 · Journal of Molecular Biology
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    • "The important role of transport processes across the plasma membrane (PM) in cell osmotic adjustment was shown for mammalian (Lang et al., 1998 and references within), bacterial (Blount and Moe, 1999; Shabala et al., 2009) and algal (Bisson and Gutknecht, 1975; Okazaki and Tazawa, 1990; Beilby et al., 1999; Shepherd and Beilby, 1999) cells. Evidence for fungi is not that numerous (Burgstaller, 1997; Lew et al., 2006) and, to the best of our knowledge, marine fungi remain essentially unexplored. "
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    ABSTRACT: A non-invasive ion-selective microelectrode technique was used to elucidate the ionic mechanisms of osmotic adjustment in a marine protist thraustochytrid. Hypoosmotic stress caused significant efflux of Na(+), Cl(-) and K(+) from thraustochytrid cells. Model calculations showed that almost complete osmotic adjustment was achieved within the first 30 min after stress onset. Of these, sodium was the major contributor (more than half of the total osmotic adjustment), with chloride being the second major contributor. The role of K(+) in the process of osmotic adjustment was relatively small. Changes in Ca(2+) and H(+) flux were attributed to intracellular signalling. Ion flux data were confirmed by growth experiments. Thraustochytrium cells showed normal growth patterns even when grown in a sodium-free solution provided the medium osmolality was adjusted by mannitol to one of the seawater. That suggests that the requirement of sodium for thraustochytrid growth cycle is due to its role in cell osmotic adjustment rather than because of the direct Na(+) involvement in cell metabolism. Altogether, these data demonstrate the evidence for turgor regulation in thraustochytrids and suggest that these cells may be grown in the absence of sodium providing that cell turgor is adjusted by some other means.
    Full-text · Article · Jul 2009 · Environmental Microbiology
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    • "Incorporation of MscL and MscS into artificial liposomal membranes has also been achieved and their functional channel activity has been recorded using the patch-clamp technique [2,6– 10]. In contrast to MscL functional studies, which to a large extent have been carried out using liposome reconstitution methods [3] [7] [11] [12], studies to date of MscS have mostly been using giant spheroplasts [13] [14] leading to a limitation in the conditions in which to study this protein. "
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    ABSTRACT: The bacterial mechanosensitive (MS) channels of small (MscS) and large (MscL) conductance have functionally been reconstituted into giant unilamellar liposomes (GUVs) using an improved reconstitution method in the presence of sucrose. This method gives significant time savings (preparation times as little as 6h) compared to the classical method of protein reconstitution which uses a dehydration/rehydration (D/R) procedure (minimum 2 days preparation time). Moreover, it represents the first highly reproducible method for functional reconstitution of MscS as well as MscS/MscL co-reconstitution. This novel procedure has the potential to be used for studies of other ion channels by liposome reconstitution.
    Full-text · Article · Jan 2009 · FEBS letters
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