Dependence of Saccharomyces cerevisiae Golgi functions on V-ATPase activity.
The V-ATPase of Saccharomyces cerevisiae is an ATP-dependent proton pump responsible for acidification of the vacuole and other internal compartments including the whole secretory pathway. We have studied the behavior of several glycoprotein processing reactions occurring in different Golgi compartments of representative vmaΔ mutants. We found that outer chain initiation is not altered in the mutants while mannosylphosphate transfer, α(1,3)-linked mannoses addition, and α factor maturation seem to be affected. The results suggest a gradation in the dependence of Golgi functions on V-ATPase activity, from early Golgi (unaffected) to late Golgi (significantly reduced). These findings are in agreement with the internal pH of Golgi cisternae measured in mammalian cells, which is more acidic in the late region. The mutant defects can be partially restored by buffering the external medium to pH 6.0, which supports the existence of a mechanism that, in the absence of a functional V-ATPase, could contribute to pH regulation at least in the late Golgi.
Department of Biomedical Sciences/Microbiology, University of Extremadura, Badajoz, Spain.
Isaac
I
Corbacho
Francisco
F
Teixidó
Isabel
I
Olivero
Luis M
LM
Hernández
D015966:Gene Expression Regulation, Fungal; D006056:Golgi Apparatus / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008358:Mannose / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D009844:Oligosaccharides / Q000378:metabolism; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*; D014617:Vacuoles / Q000201:enzymology*
D009844:Oligosaccharides; D029701:Saccharomyces cerevisiae Proteins; D025262:Vacuolar Proton-Translocating ATPases; D008358:Mannose