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Ionic concentration in MscS

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Bacterial cells, like those of Escherichia coli, protect themselves against sudden inside-out pressure differences that arise osmotically from changes in a cell's environment and that could burst the cellular envelop. The protection is achieved through so-called mechanosensitive channels in the cell membrane.  One such channel, that dissipates like a safety valve pressure differences across the Escherichia coli cell membrane, is contributed by the protein MscS.  Upon tension in the cell membrane, that can also be applied systematically in the laboratory, the channel opens and permits molecules to pass, as best measured through an ion current leaking through the stretched membrane.  MscS is a channel with a balloon-like filter,  the function of the latter being still a mystery  (see Nov 2004 highlight, "Japanese lantern protein").  Now computational biologists using NAMD teamed up with device engineers using BioMoca to study MscS as reported recently.  The team monitored the mysterious MscS computationally over several microseconds, a record time for protein simulations.  MscS was found to permit water passage, but to also exhibit strong electrostatic forces that focus ions streaming through its filter balloon and channel.  This suggests MscS to be both a hydrostatic and an electrical safety valve.  Even though now better known, MscS' entire function remains shrouded in mystery (more on our MscS web site).