Fast rafting

Ever since the introduction of the fluid mosaic model, proteins have been viewed as rather hyperactive ships in a sea of lipids. Cholesterol-rich rafts were thought to be at least a partial exception to this trend. Although raft proteins move, their movement was predicted to be dampened by their inclusion in rafts, which act as stages for signaling.

Now, Kenworthy et al. have tested this idea directly (page 735). They used fluorescence recovery after photobleaching (FRAP) to follow green fluorescent protein (GFP)-tagged raft and nonraft proteins. The team then calculated the diffusion coefficients of the tested molecules. They found that raft-associated proteins and those not bound to rafts move similarly—neither faster nor slower.

This conflicts with some studies using single-particle tracking. There are several possible explanations for the new data....