FIGURE 4.

Ac45 mutant proteins differentially affect endogenous V-ATPase localization. A–D, immunogold labeling of ultra-thin pituitary cryosections with anti-GFP antibody confirmed the expression of the GFP/Ac45 mutant transgene products at the plasma membrane of the transgenic Xenopus melanotrope cells. No labeling was found in wild-type cells. E–H, immunogold labeling with an anti-V₁A antibody showed that in the cleaved-Ac45 and Ac45 ΔC transgenic melanotrope cells the endogenous V-ATPase is recruited to the plasma membrane but not in wild-type cells nor in transgenic cells expressing cleaved-Ac45ΔC. White arrow, smooth plasma membrane; black arrow, microvillar plasma membrane; N, nucleus; ER, endoplasmic reticulum.