Binding of NAP-22, a calmodulin-binding neuronal protein,to raft-like domains in model membranes |
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Authors: | Khan Tapan K Yang Bing Thompson Nancy L Maekawa Shohei Epand Richard M Jacobson Ken |
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Affiliation: | Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA. |
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Abstract: | The cholesterol-binding protein NAP-22 is a major component of the detergent-insoluble low-density fraction of rat brain. In this study, we found, using fluorescence microscopy, that native NAP-22, but not a demyristoylated form, binds to cholesterol-rich raft-like domains in planar-supported monolayers and remains bound after nonionic detergent extraction. NAP-22 also protects the cholesterol-rich domains during extraction by methyl-beta-cyclodextrin. The lateral mobility of this protein is much lower than that of other raft components in model membranes, suggesting that both cholesterol binding and inter-NAP-22 interactions markedly reduce its lateral diffusion. This study suggests that NAP-22 binding may be employed to image cholesterol-rich regions, such as caveolae/rafts, on the plasma membrane of cells, and preliminary efforts in that direction are presented. |
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