USE OF MONOCLONAL-ANTIBODIES TO STUDY THE STRUCTURE AND FUNCTION OF EUKARYOTIC PROTEIN-SYNTHESIS INITIATION-FACTOR EIF-2B

The eukaryotic protein synthesis initiation factor, eIF-2B, is a multi meric protein of five different subunits termed alpha, beta, gamma, de lta and epsilon, which facilitates recycling of a further factor, eIF- 2, and is an important control point in the initiation process. In ord er to investigate the structure and function of eIF-2B, monoclonal ant ibodies have been prepared to the beta, delta and epsilon subunits of the factor from rabbit reticulocytes. All three antibodies are active in Western blotting, ELISA and immunoprecipitation. The anti-epsilon a ntibody inhibits both the guanine nucleotide exchange activity of eIF- 2B and protein synthesis in the rabbit reticulocyte lysate at the leve l of initiation. The other two antibodies do not inhibit either guanin e nucleotide exchange or protein synthesis. The monoclonal antibodies and a polyclonal anti-(rabbit reticulocyte eIF-2B) serum were used to investigate the subunit size and the antigenic structure of eIF-2B fro m a variety of rabbit tissues and from a variety of mammalian species. eIF-2B from all rabbit tissues tested was indistinguishable from that prepared from rabbit reticulocytes. Quantitative studies showed subst antial variation in the relative concentrations of eIF-2 and eIF-2B be tween different rabbit tissues. Marked variation in both the sizes of the subunits and their reaction with the antibodies was observed betwe en eIF-2B from rabbit, rat, guinea pig and man.