2-DIMENSIONAL MAPPING OF THE ENDOGENOUS PROTEINS OF THE RAT HEPATOCYTE GOLGI-COMPLEX CLEARED OF PROTEINS IN TRANSIT

The discovery of additional endogenous Golgi proteins will lead to sig nificant new insights into Golgi function. To this end, stacked Golgi fractions (SGFs) were isolated from rat liver before (CTL SGF) and aft er molecules in transit through the Golgi were cleared by pre-treatmen t with cycloheximide (CHX SGF). Electron microscopic (ISM) morphometri c and biochemical analyses showed that the in vivo stacked morphology is retained, that > 90% of the elements can be positively identified a s Golgi stacks and cisternae, and that transmembrane protein markers o f the Golgi complex are enriched 300- to 800-fold over starting postnu clear supernatant (PNS) [24]. High-resolution two-dimensional (2-D) ge l mapping has been carried out on the CTL PNS, CTL SII (an intermediat e fraction), CTL SGF, CHX SGF, CHX SGF-high pH supernatant, and CHX SG F-high pH pellet. This analysis, coupled with immunoblotting and align ment of the 2-D gels with master gels, has allowed the identification of a number of known proteins and the preliminary characterization of the most abundant 173 Golgi-specific proteins. These 173 proteins have been placed into three categories: targe, cytosolic Golgi-associated, and resident Golgi proteins. These categories are tentative and will be modified as more data are acquired from immunoblotting and protein sequencing.