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Dynamic Patches of Membrane Proteins

Yael Lavi ^*, Michael A. Edidin  and Levi A. Gheber ^*

^* Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel; and Department of Biology, Johns Hopkins University, Baltimore, Maryland USA

Correspondence: Address reprint requests and inquiries to Levi A. Gheber, E-mail: glevi{at}bgu.ac.il.

We test here a previously proposed hypothesis about lateral heterogeneity of cell membranes, a model predicting that heterogenity is maintained by a combination of delivery and intake of molecules with barriers to lateral free diffusion. To test the validity of the model, we observed green florescent protein tagged major histocompatibility complex class I patches on the plasma membrane of mouse fibroblasts, using total internal reflection fluorescence microscopy in real time. The dynamic characterization revealed the life course of these patches comprises delivery of molecules at a short instant, followed by a slow, exponential decay, corresponding to diffusion of the molecules over dynamic barriers to free lateral diffusion. The characteristic lifetime of the patches, extracted from the measurements, is 30 s, in excellent agreement with the predictions of the model.