GTP‐induced fusion of isolated pancreatic microsomal vesicles is increased by acidification of the vesicle lumen

FEBS Letters

Schulz, Irene¹  Hampe, Wolfgang¹  Zimmermann, Petra¹ 

[1] Max-Planck-Institut für Biophysik, Kennedyallee 70, 6000 Frankfurt (Main 70, FRG

关键词: Proton-gradient;    Energy transfer;    Light scatter;    Acridine orange;    H+-ATPase;    Bafilomycin B1;   

DOI  :  10.1016/0014-5793(90)80372-P

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Using the ‘fusogen’ polycthyleneglycol (PEG), Dawson et al. [1] have concluded that both guanosine triphosphate (GTP)-mduced calcium efflux and the enhancement of IP₃-promoted calcium release from rat liver microsomal vesicles could be attributed to a GTP-dependent vesicle fusion. We have studied GTP-induced fusion of microsomal vesicles from rat exocrine pancreas using light scatter and fluorescence dequenching methods. In the presence of PEG (3%), GTP (10 μM) induced a decrease in light scatter and an increase in fluorescence in the fluorescence dequenching assay (GTP-effect) indicating fusion of the vesicles. Guanosine 5'-O-(3-thiotriphosphate) (10 μM) had no effect on its own and inhibited the GTP-induced signals. Preincubation of the vesicles with adenosine triphosphate (ATP) (4 mM) increased the GTP-effect by 80%. whereas bafilomycin B₁, a specific inhibitor of vacuolar type H⁺-ATPases, and the protonophore CCCP (10 μM) inhibited only the ATP-dependent part of the GTP-effect. Inhibitors of the vacuolar type H⁺ -ATPase, which are also SH-alkylating reagents such as N-ethylmaleimid (100 μM) and the tyrosine-,cysteinc- and lysine-reactive reagent 7-chloro-4-nitrobenz-2-exa-1,3-diazole (10 μM) [2,3j. abolished the GTP-effect in the absence or presence of ATP. We conclude that GTP induces fusion of pancreatic microsomes which is increased by an H⁺ gradient established by a vacuolar type H⁺-ATPase.

【 授权许可】

Unknown