This project involves studies of the structures, functions and mechanisms of action of members of the superfamily of regulatory GTP binding proteins; particularly the members of the ADP-ribosylation factor (ARF) family. ARF has been shown to have essential functions in the maintenance of the integrity and proper functioning of the endoplasmic reticulum, Golgi complex, and endosome compartments. ARF proteins also stimulate phospholipase D, likely serving as the direct activators of this effector. There are currently 6 mammalian ARF proteins and 6 mammalian ARF-like proteins fully cloned and sequenced. The cloning and sequencing of novel members of this family has slowed to allow more time to analyze functions of the known members. We have utilized a number of functional screens in yeast to provide new clues to the actions of ARF proteins in eukaryotes. These screens have included suppressor analysis, a conditional lethal screen of ARF1, and two-hybrid screening to identify other components in ARF signaling pathways. Each of these approaches have led to the cloning of human and yeast genes whose products interact with Arf proteins. Results of these analysis are likely to open up new areas of research into this increasingly important family of cellular regulators. The three dimensional crystal structure of ARF GDP has been solved. Work continues on the active, ARF GTP and myristoylated ARF structures as each should aid in the determination of critical functional domains and design of specific inhibitors of different Arf activities.
