Colombo M I, Mayorga L S, Casey P J, Stahl P D
Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, MO 63110.
Science. 1992 Mar 27;255(5052):1695-7. doi: 10.1126/science.1348148.
Guanosine triphosphate (GTP)-binding proteins are required for intracellular vesicular transport. Mastoparan is a peptide component of wasp venom that increases nucleotide exchange in some classes of G alpha subunits of regulatory heterotrimeric GTP-binding proteins (G proteins). Mastoparan and other compounds that increase nucleotide exchange by G proteins inhibited endosome fusion in vitro and reversed the effects of guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S), a nonhydrolyzable GTP analog. Addition of beta gamma subunits of G proteins to the fusion assay antagonized the stimulatory effect of GTP-gamma-S, confirming the participation of G proteins. These results indicate that GTP-binding proteins are required for endosome fusion and in particular that a G protein is involved. Given the function of G proteins in signal transduction, these findings may provide insight into the mechanism by which endosomal vesicles become competent for fusion after their formation at the cell surface.
三磷酸鸟苷（GTP）结合蛋白是细胞内囊泡运输所必需的。马斯托帕兰是黄蜂毒液的一种肽成分，它能增加某些调节性异三聚体GTP结合蛋白（G蛋白）的Gα亚基中的核苷酸交换。马斯托帕兰和其他能增加G蛋白核苷酸交换的化合物在体外抑制内体融合，并逆转了不可水解的GTP类似物5'-O-（3-硫代三磷酸）鸟苷（GTP-γ-S）的作用。将G蛋白的βγ亚基添加到融合试验中可拮抗GTP-γ-S的刺激作用，证实了G蛋白的参与。这些结果表明，GTP结合蛋白是内体融合所必需的，特别是有一个G蛋白参与其中。鉴于G蛋白在信号转导中的功能，这些发现可能有助于深入了解内体囊泡在细胞表面形成后变得能够融合的机制。
