Fig. 2.
Immobile ABCA1 exists as dimers. (A) Time-dependent changes of the fluorescence intensity of a representative spot of ABCA1 fused with mEGFP in the PM showing two-step photobleaching. As EGFP is reported to have a weak tendency to dimerize (33), we examined whether EGFP is involved in ABCA1 dimerization. The ratio of two-step photobleaching of immobile spots of ABCA1 fused with EGFP was not significantly different (P = 0.3613) compared with that of ABCA1 fused with mEGFP, suggesting that ABCA1 dimerization is not due to EGFP. Representative images of an individual spot before and after photobleaching are shown above the graph. Arrows indicate photobleaching dips in the fluorescence intensity. (B–D) Distributions of D100ms for ABCA1-EGFP spots (B), ABCA1-MM–EGFP spots (C), and ABCA1-EGFP spots 10–15 min after apoA-I addition (D).