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Catalysis of guanine nucleotide exchange on eIF-2 by eIF-2B: is it a sequential or substituted enzyme mechanism?
1Department of Biochemistry, University of the Witwatersrand, Johannesburg, South Africa.
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.
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