2eqb | pdb_00002eqb
Crystal structure of the Rab GTPase Sec4p, the Sec2p GEF domain, and phosphate complex
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Overview
Vesicular transport during exocytosis is regulated by Rab GTPase (Sec4p in, yeast), which is activated by a guanine nucleotide exchange factor (GEF), called Sec2p. Here, we report the crystal structure of the Sec2p GEF, domain in a complex with the nucleotide-free Sec4p at 2.7 A resolution., Upon complex formation, the Sec2p helices approach each other, flipping, the side chain of Phe-109 toward Leu-104 and Leu-108 of Sec2p. These three, residues provide a hydrophobic platform to attract the side chains of, Phe-49, Ile-53, and Ile-55 in the switch I region as well as Phe-57 and, Trp-74 in the interswitch region of Sec4p. Consequently, the switch I and, II regions are largely deformed, to create a flat hydrophobic interface, that snugly fits the surface of the Sec2p coiled coil. These drastic, conformational changes disrupt the interactions between switch I and the, bound guanine nucleotide, which facilitates the GDP release. Unlike the, recently reported 3.3 A structure of the Sec4p.Sec2p complex, our, structure contains a phosphate ion bound to the P-loop, which may, represent an intermediate state of the nucleotide exchange reaction.
About this Structure
2EQB is a Protein complex structure of sequences from Saccharomyces cerevisiae with PO4 as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structure of the Sec4p{middle dot}Sec2p complex in the nucleotide exchanging intermediate state., Sato Y, Fukai S, Ishitani R, Nureki O, Proc Natl Acad Sci U S A. 2007 May 15;104(20):8305-10. Epub 2007 May 8. PMID:17488829
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