PROTEIN INTERACTIONS REGULATING VESICLE TRANSPORT BETWEEN THE ENDOPLASMIC-RETICULUM AND GOLGI-APPARATUS IN MAMMALIAN-CELLS

The proposed cis-Golgi vesicle receptor syntaxin 5 was found in a comp lex with Golgi-associated SNARE of 28 kDa (GOS-28), rbet1, rsly1, and two novel proteins characterized herein: rat sec22b and membrin, both cytoplasmically oriented integral membrane proteins. The complex appea rs to recapitulate vesicle docking interactions of proteins originatin g from distinct compartments, since syntaxin 5, rbet1, and GOS-28 loca lize to Golgi membranes, whereas mouse sec22b and membrin accumulate i n the endoplasmic reticulum. Protein interactions in the complex are d ramatically rearranged by N-ethylmaleimide-sensitive factor. The compl ex consists of two or more subcomplexes with some members (rat sec22b and syntaxin 5) in common and others (rbet1 and GOS-28) mutually exclu sively associated. We propose that these protein interactions determin e vesicle docking/fusion fidelity between the endoplasmic reticulum an d Golgi.