FIGURE 4.
Membrane-targeted CaVβ2a also forms dimers. A, fluorescence emission spectra of living tsA210 cells expressing the indicated CFP- and YFP-tagged CaVβ2a constructs either separately or together (co-transfection). Mix corresponds to the emission spectra of a mixture of single transfected cells (mix). Emission spectra were collected at excitation wavelength λexc = 440 nm. a.u., arbitrary units. B, distribution and quantitative pixel-based FRET analysis of CFP-and YFP-tagged CaVβ2a in living tsA210 cells. Scale bar, 5 μm. EfD, apparent FRET efficiency, mem, membrane-localized CaVβ2a; intra, intracellular-localized CaVβ2a. Data represent mean values ± S.E. (n = 6). C, BN-PAGE analysis of CaVβ2a. Lanes 1–4 were loaded with CaVβ2a and lanes 5 and 6 with the CaVβ2a concatamer. In the absence of SDS, the CaVβ2a concatamer is poorly resolved (lane 5). Samples were treated as indicated at the bottom of the panel. D, BN-PAGE analysis of CaVβ2a C113A. Lanes 1–4 were loaded with CaVβ2a C113A and lanes 5 and 6 were loaded with the CaVβ2a concatamer.