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          Institute: MPI für biophysikalische Chemie     Collection: Ehemalige Abteilungen     Display Documents

ID: 16690.0, MPI für biophysikalische Chemie / Ehemalige Abteilungen
Significance of GTP hydrolysis in Ypt1p-regulated endoplasmic reticulum to Golgi transport revealed by the analysis of two novel Ypt1-GAPs
Authors:De Antoni, A.; Schmitzova, J.; Trepte, H. H.; Gallwitz, D.; Albert, S.
Date of Publication (YYYY-MM-DD):2002-10-25
Title of Journal:Journal of Biological Chemistry
Issue / Number:43
Start Page:41023
End Page:41031
Review Status:Peer-review
Audience:Not Specified
Abstract / Description:We here report on the identification and detailed biochemical characterization of two novel GTPase-activating proteins, Gyp5p and Gyp8p, whose efficient substrate is Ypt1p, a Ypt/Rab-GTPase essential for endoplasmic reticulum-to-Golgi trafficking in yeast. Gyp5p, accelerated the intrinsic GTPase activity of Ypt1p 4.2 X 10(4)-fold and, surprisingly, the 40-fold reduced GTP hydrolysis rate of Ypt1 (Q67L)p 1.5 x 10(4)-fold. At steady state, the two newly discovered GTPase-activating proteins (GAPs) as well as the previously described Gyp1p, which also uses Ypt1p as the preferred substrate, display different sulicellular localization. To add to an understanding of the significance of Ypt1p-bound GTP hydrolysis in vivo, yeast strains expressing the GTPase-deficient Ypt1(Q67L)p and having different Ypt1-GAP genes deleted were created. Depending on the genetic background, different mutants exhibited growth defects at low temperature and, already at permissive temperature, various morphological alterations resembling autophagy. Transport of proteins was not significantly impaired. Growth defects of Ypt1(Q67L)expressing cells could be suppressed on high expression of all three Ypt1-GAPs. We propose that permanently active Ypt1p leads to increased vesicle fusion, which might induce previously unnoticed autophagic degradation of exaggerated membrane-enclosed structures. The data indicate that hydrolysis of Ypt1p-bound GTP is a prerequisite for a balanced vesicle flow between endoplasmic reticulum and Golgi compartments.
Comment of the Author/Creator:Date: 2002, OCT 25
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für biophysikalische Chemie/Abt. Dieter Gallwitz / 150
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