Biophysics

Polar Preferences

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Science  09 May 2008:
Vol. 320, Issue 5877, pp. 718
DOI: 10.1126/science.320.5877.718c

In rod-shaped bacteria, proteins that mediate chemotaxis, cell division, and development are observed to localize to the poles. Recent evidence of heterogeneity in the composition of the bacterial cytoplasmic membrane and of the preferential binding of proteins to particular lipids suggests that membrane architecture may contribute to protein localization. For example, cardiolipin is involved in the polar and septal targeting of the Escherichia coli osmosensory transporter ProP. Cardiolipin is a phospholipid with high intrinsic curvature, and one proposal is that clusters of cardiolipin localize spontaneously to the poles, where the membrane is constrained by the curved cell wall. Mukhopadhyay et al. have extended their quantitative biophysical model to include the elastic energy of the membrane (which penalizes a deformation of the membrane away from the cell wall-imposed geometry), the interaction energy between lipids, and entropy. They show that variations in osmotic pressure, the force that pins the membrane to the cell wall, can regulate localization. The model predicts the minimum membrane fraction of cardiolipin required for domain formation and a polar localization that are consistent with the experimentally observed critical concentration of cardiolipin required for polar localization of ProP. — VV

Biophys. J. 94, 10.1529/biophysj.107.126920 (2008).

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