GMx33: a novel family of trans-Golgi proteins identified by proteomics |
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Authors: | Wu C C Taylor R S Lane D R Ladinsky M S Weisz J A Howell K E |
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Affiliation: | Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver, Colorado, USA;Laboratory for 3D Fine Structure, University of Colorado at Boulder, Boulder, Colorado, USA |
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Abstract: | The known functions of the Golgi complex include the sorting, packaging, post-translational modification, and transport of secretory proteins, membrane proteins, and lipids. Other functions still remain elusive to cell biologists. With the goal of identifying novel Golgi proteins, a proteomics project was undertaken to map the major proteins of the organelle using two-dimensional gels, to identify the unknowns using tandem mass spectrometry, and to screen for Golgi residents using GFP-fusion constructs. Multiple unknowns were identified, and the initial characterization of one of these proteins is reported here. GMx33α is a member of a conserved family of cytosolic Golgi-associated proteins with no known homology to any known functional domain or protein. Biochemical analyses show that GMx33α differentially partitions into all phases of multiple detergent extractions, and two-dimensional immunoblots reveal that there are multiple differentially modified forms of GMx33α associated with the Golgi, several of which are phosphorylated. Evidence suggests that these post-translational modifications regulate its association with the Golgi. GMx33α was not found on Golgi budded vesicles, and immuno-electron microscopy co-localizes GMx33α to the trans -face on the same three cisternae as TGN38 in normal rat kidney cells. This work represents the preliminary characterization of a novel family of trans -Golgi-associated proteins. |
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Keywords: | Detergent solubility immuno-EM peripheral Golgi protein proteomics trans-Golgi network two-dimensional gel electrophoresis |
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