Small membrane raft

Membrane rafts and caveolae sequester groups of signaling proteins in small regions of the plasma membrane, enhancing their interactions and making signaling more efficient. 

Engulfing a Small Partide with a Membrane Raft... 

The most likely way for pardaxin molecules to insert across the membrane in an antiparallel manner is for them to form antiparallel aggregates on the membrane surface that then insert across the membrane. We developed a "raft"model (data not shown) that is similar to the channel model except that adjacent dimers are related to each other by a linear translation instead of a 60 rotation about a channel axis. All of the large hydrophobic side chains of the C-helices are on one side of the "raft" and all hydrophilic side chains are on the other side. We postulate that these "rafts" displace the lipid molecules on one side of the bilayer. When two or more "rafts" meet they can insert across the membrane to form a channel in a way that never exposes the hydrophilic side chains to the lipid alkyl chains. The conformational change from the "raft" to the channel structure primarily involves a pivoting motion about the "ridge" of side chains formed by Thr-17, Ala-21, Ala-25, and Ser-29. These small side chains present few steric barriers for the postulated conformational change. 

The membrane-associated small G proteins H-Ras and K-Ras have been studied with respect to their association with cytoplasmic leaflets. These two proteins have nearly identical structures and functions but different membrane anchors, membrane distributions and effector responses. Application of the FRAP method to fluorescent constructs of H-Ras and K-Ras revealed that only H-Ras in its guanosine 5 diphosphate (GDP)-bound form associates with cholesterol-dependent rafts [26]. 

Pralle, A., Keller, P., Florin, E.L., Simons, K., Horber, J.K.H. Sphingolipid-cholesterol rafts diffuse as small entities in the plasma membrane of mammalian cells. J Cell Biol 148 (2000)... 

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