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Traffic. 2000 Dec;1(12):963-75.

GMx33: a novel family of trans-Golgi proteins identified by proteomics.

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1
Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver, Colorado, USA.

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. GMx33 alpha 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 GMx33 alpha differentially partitions into all phases of multiple detergent extractions, and two-dimensional immunoblots reveal that there are multiple differentially modified forms of GMx33 alpha associated with the Golgi, several of which are phosphorylated. Evidence suggests that these post-translational modifications regulate its association with the Golgi. GMx33 alpha was not found on Golgi budded vesicles, and immuno-electron microscopy co-localizes GMx33 alpha 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.

PMID:
11208086
[Indexed for MEDLINE]
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