FIGURE 2.

Interaction of VDAC2 with StAR. A, chemical cross-linking of the purified rat testis MAM with BS3 followed by Western blotting with StAR and VDAC2 antibodies independently. B and C, identification of the MAM-interacting proteins. Purified MAM was incubated with the chemical cross-linker BS3, immunoprecipitated, and then analyzed by Western blotting independently with the indicated antibodies. Fetal bovine serum (FBS) was used as a negative control to show the specificity of StAR and VDAC2 antibodies. D, co-immunoprecipitation (Co-IP) of the indicated antibodies followed by Western blotting with a StAR antibody (Ab). E, panels a–c, determination of the localization of the different MAM-associated proteins of rat testes using sucrose density gradient analysis of the digitonin-lysed mitochondrial complexes after 1 (solid squares) and 4 (solid triangles) h of ultracentrifugation. Each fraction was probed with the indicated antibodies, and the distribution of the proteins was graphed. Data presented are the mean ± S.E. (error bars) of three independent experiments. StAR was associated for a limited time of 1 h with all the MAM-associated proteins analyzed. The bottom panels are the Western blots prior to cross-linking showing an equivalent loading in each lane.