National Center for
4LI0: Crystal Structure Of Gdp-bound Rab8:grab
Intermediates in the Guanine Nucleotide Exchange Reaction of Rab8 Protein Catalyzed by Guanine Nucleotide Exchange Factors Rabin8 and GRAB
J. Biol. Chem. (2013) 288 p.32466-32474
Small G-proteins of the Ras superfamily control the temporal and spatial coordination of intracellular signaling networks by acting as molecular on/off switches. Guanine nucleotide exchange factors (GEFs) regulate the activation of these G-proteins through catalytic replacement of GDP by GTP. During nucleotide exchange, three distinct substrate.enzyme complexes occur: a ternary complex with GDP at the start of the reaction (G-protein.GEF.GDP), an intermediary nucleotide-free binary complex (G-protein.GEF), and a ternary GTP complex after productive G-protein activation (G-protein.GEF.GTP). Here, we show structural snapshots of the full nucleotide exchange reaction sequence together with the G-protein substrates and products using Rabin8/GRAB (GEF) and Rab8 (G-protein) as a model system. Together with a thorough enzymatic characterization, our data provide a detailed view into the mechanism of Rabin8/GRAB-mediated nucleotide exchange.