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| Subject Categories: Membranes & Transport | Microbiology & Pathogens |
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| The EMBO Journal
(2002) 21, 5323–5330, doi: 10.1093/emboj/cdf537 |
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| Ionic regulation of MscK, a mechanosensitive channel from Escherichia coli |
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| Yuezhou Li1, Paul C. Moe1, Subramanian Chandrasekaran2, 3, Ian R. Booth2 and Paul Blount1 |
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1 Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA 2 Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK 3 Present address: Division of Biochemistry, University of Manchester, 2.205 Stopford Building, Oxford Road, Manchester M13 9PT, UK To whom correspondence should be addressed Paul Blount, Paul.Blount@UTSouthwestern.edu Received 30 July 2002; Revised 19 August 2002; Accepted 21 August 2002. |
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| Abstract |
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| Three gene products that form independent mechanosensitive channel activities have been identified in Escherichia coli. Two of these, MscL and MscS, play a vital role in allowing the cell to survive acute hypotonic stress. Much less is known of the third protein, MscK (KefA). Here, we characterize the MscK channel activity and compare it with the activity of its structural and functional homologue, MscS. While both show a slight anionic preference, MscK appears to be more sensitive to membrane tension. In addition, MscK, but not MscS activity appears to be regulated by external ionic environment, requiring not only membrane tension but also high concentrations of external K+, NH4+, Rb+ or Cs+ to gate; no activity is observed with Na+, Li+ or N-methyl-D-glucamine (NMDG). An MscK gain-of-function mutant gates spontaneously in the presence of K+ or similar ions, and will gate in the presence of Na+, Li+ and NMDG, but only when stimulated by membrane tension. Increased sensitivity and the highly regulated nature of MscK suggest a more specialized physiological role than other bacterial mechanosensitive channels. |
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| Keywords: MscL, MscS, osmoregulation, stretch-activated channels, turgor maintenance |
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