Characterization of Arf4•GDP

Abstract

In this thesis, I characterized the association of Arf4•GDP with ER-Golgi intermediate compartment membranes. We confirmed that GDP-arrested Arf4 mutants associated with membranes irrespective of nature of tag or mutation. Recruitment appeared specific since loss of N-terminal myristoylation abolished binding. Surprisingly, mutations of residues unique to class II Arfs did not prevent recruitment of Arf4 to peripheral puncta. We then examined the failure of the GDP-arrested Arf4 mutant to disrupt Golgi structure. We identified residues R79 and E113 (likely involved in salt bridge interaction) only present in Arf1 and Arf5 as critical to the ability of their GDP-arrested mutants to disrupt Golgi structure. As predicted, introduction of these residues transformed Arf4•GDP into a dominant negative mutant. Interestingly, overexpression of the putative Arf•GDP receptor membrin prevented the effects of dominant negative Arf1 but not dominant negative Arf4. These results will facilitate identification of a novel Arf target critical to protein trafficking.