Dual Interaction of ADP Ribosylation Factor 1 with Sec7 Domain and with Lipid Membranes during Catalysis of Guanine Nucleotide Exchange

• Published in: The Journal of biological chemistry Vol. 274; no. 53; pp. 37629 - 37636
• Main Authors: Béraud-Dufour, S, Paris, S, Chabre, M, Antonny, B
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 31-12-1999
• Subjects: ADP-Ribosylation Factor 1 - chemistry; ADP-Ribosylation Factor 1 - metabolism; Catalysis; Fungal Proteins - metabolism; Guanine Nucleotide Exchange Factors - metabolism; Life Sciences; Liposomes; Membrane Lipids - metabolism; Protein Binding
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.53.37629

Sec7 domains catalyze the replacement of GDP by GTP on the G protein ADP-ribosylation factor 1 (myrARF1) by interacting with
its switch I and II regions and by destabilizing, through a glutamic finger, the β-phosphate of the bound GDP. The myristoylated
N-terminal helix that allows myrARF1 to interact with membrane lipids in a GTP-dependent manner is located some distance from
the Sec7 domain-binding region. However, these two regions are connected. Measuring the binding to liposomes of functional
or abortive complexes between myrARF1 and the Sec7 domain of ARNO demonstrates that myrARF1, in complex with the Sec7 domain,
adopts a high affinity state for membrane lipids, similar to that of the free GTP-bound form. This tight membrane attachment
does not depend on the release of GDP induced by the Sec7 domain but is partially inhibited by the uncompetitive inhibitor
brefeldin A. These results suggest that the conformational switch of the N-terminal helix of myrARF1 to the membrane-bound
form is an early event in the nucleotide exchange pathway and is a prerequisite for a structural rearrangement at the myrARF1-GDP/Sec7
domain interface that allows the glutamic finger to expel GDP from myrARF1.