Instant Death

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Science  17 Aug 2001:
Vol. 293, Issue 5533, pp. 1223
DOI: 10.1126/science.293.5533.1223d

Bacteriophages produce small proteins called holins, which, at a defined point in the infection cycle, punch holes in bacterial cell membranes. After the accumulation of a critical number of holin molecules in the cell membrane, oligomerization is triggered, causing cell lysis. Bacteria can be tethered to a substrate by antibodies directed against their flagella, and their cell bodies will then rotate. The rate of this rotation is proportional to the proton motif force (pmf) of the bacterial cell membrane and is a measure of membrane integrity.

Gruendling et al. saw that in phage-infected bacteria, rotation stops abruptly a few seconds before catastrophic cell lysis. Apparently, the pmf keeps the holins apart until the threshold concentration is reached, when they instantaneously clump to form a weak patch in the membrane. This collapses the pmf and causes membrane rupture. However, the holin's target in the membrane remains unknown, and the mechanism of action of these hugely diverse and ancient clock-like proteins remains elusive. — CA

Proc. Natl. Acad. Sci. U.S.A.98, 9348 (2001).

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