Friday, December 28, 2007

bacterial hair styles

... well, ok, let's return to some science for a change.

Many pathogenic bacteria, e.g. those that cause infections of the urinary tract, have very thin "hairs" allowing them to stick to cells of their host. Thanks to these hairs, bacteria can invade the urinary tract and avoid being flushed out with the urine. These are known as pili, and their protein subunits are stuck together like lego bricks, i.e. one end has a binding pocket, and the other has a spare bit of protein chain that fits in there, and contributes one strand to the beta-sheet fold.

Before they get assembled into this pile of lego bricks, the subunits are bound to molecular chaperones in the periplasm, which use the same binding mechanism. So how does the subunit get handed over from the chaperone to the neighbouring chaperone? Emanuele Paci and co-workers at Leeds and Gabriel Waksman's group at Birkbeck college London have now presented molecular dynamics simulation that support the so called zip-in zip-out mechanism, which involves one beta sheet opening up like a zip, and the other starting to zip up in a coordinated fashion. Which is just beautiful molecular ballet.

But it is also useful, as potential drugs that can stop pili from growing may soon become an attractive alternative to antibiotics. As they disarm bacteria rather than killing them, the hope is that they will not favour the evolution of resistant strains quite as much as antibiotics do, plus they give the immune system a better chance to train its forces against the bacteria.

The paper comes out in Journal of Molecular Biology, and with luck you may be able to read it via
Science Direct.

I've also written a full-length feature on this topic in German, which is due to appear in February.
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