title: Catalysis of guanine nucleotide exchange on eIF-2 by eIF-2B: is it a sequential or substituted enzyme mechanism?
abstract: The mechanism of action of the eukaryotic initiation factor eIF-2B in catalyzing the exchange of guanine nucleotides bound to eIF-2 is uncertain--evidence having been adduced for a sequential mechanism and for a substituted enzyme mechanism. Data purporting to support a substituted enzyme mechanism have been analysed and shown to be ambiguous and equally consistent with a sequential mechanism. Suitable rate constants for a sequential mechanism involving the transient formation of the quaternary complex eIF-2.eIF-2B.GDP.GTP are suggested.
authors.affiliation: Department of Biochemistry, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: K L
authors.initials: KL
authors.lastname: Manchester
mesh_terms: D002384:Catalysis; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism*; D007700:Kinetics; D008956:Models, Chemical; D011506:Proteins / Q000378:metabolism*
chemical_list: D015852:Eukaryotic Initiation Factor-2; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D006153:Guanosine Diphosphate