Is there a need for channelling in the functioning of the protein synthesis initiation factors eIF-2 and eIF-2B?

The possibility that channelling is necessary in the initiation of eukaryotic protein synthesis is evaluated. Calculations suggest that despite the very high association rate constant found for the interaction of eIF-2 and eIF-2B under in vitro conditions, it is unlikely that rates in vivo can be high enough to permit measured rates of protein synthesis. Channelling therefore seems a priori a requirement.