title: Crystal structure of ARF1*Sec7 complexed with Brefeldin A and its implications for the guanine nucleotide exchange mechanism.
abstract: ARF GTPases are activated by guanine nucleotide exchange factors (GEFs) of the Sec7 family that promote the exchange of GDP for GTP. Brefeldin A (BFA) is a fungal metabolite that binds to the ARF1*GDP*Sec7 complex and blocks GEF activity at an early stage of the reaction, prior to guanine nucleotide release. The crystal structure of the ARF1*GDP*Sec7*BFA complex shows that BFA binds at the protein-protein interface to inhibit conformational changes in ARF1 required for Sec7 to dislodge the GDP molecule. Based on a comparative analysis of the inhibited complex, nucleotide-free ARF1*Sec7 and ARF1*GDP, we suggest that, in addition to forcing nucleotide release, the ARF1-Sec7 binding energy is used to open a cavity on ARF1 to facilitate the rearrangement of hydrophobic core residues between the GDP and GTP conformations. Thus, the Sec7 domain may act as a dual catalyst, facilitating both nucleotide release and conformational switching on ARF proteins.
authors.affiliation: Howard Hughes Medical Institute, Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Mossessova
authors.forename: Richard A
authors.initials: RA
authors.lastname: Corpina
authors.forename: Jonathan
authors.initials: J
authors.lastname: Goldberg
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D020126:Brefeldin A / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000737:chemistry / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D011500:Protein Synthesis Inhibitors / Q000737:chemistry* / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D046911:Macromolecular Substances; D011500:Protein Synthesis Inhibitors; C066755:Sec7 guanine nucleotide exchange factors; D006153:Guanosine Diphosphate; D020126:Brefeldin A; D006160:Guanosine Triphosphate; D020823:ADP-Ribosylation Factor 1