title: Catalysis of guanine nucleotide exchange on eIF2 by eIF2B: can it be both a substituted enzyme and a sequential mechanism?
abstract: There are conflicting reports over the question of whether the displacement by GTP of GDP bound to eIF2 catalyzed by eIF2B follows a substituted enzyme mechanism, as is believed to be the case for other guanine nucleotide exchange factors, or is a sequential mechanism. Analysis of data recently provided by Williams et al. (J. Biol. Chem. 276, 24697-24703, 2001) showing displacement by eIF2B of GDP bound to eIF2 in the absence of displacing nucleotide appears to offer a way of resolving the dispute and suggests that both mechanisms may be operative.
authors.affiliation: School of Molecular and Cell Biology, University of the Witwatersrand, Wits 2050, Johannesburg, South Africa. 089manch@cosmos.wits.ac.za
authors.forename: K L
authors.initials: KL
authors.lastname: Manchester
mesh_terms: D002384:Catalysis; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D020717:Eukaryotic Initiation Factor-2B / Q000737:chemistry / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008956:Models, Chemical
chemical_list: D015852:Eukaryotic Initiation Factor-2; D020717:Eukaryotic Initiation Factor-2B; D006160:Guanosine Triphosphate