INTERACTIONS AMONG 4 SUBUNITS OF ELONGATION-FACTOR-1 FROM RICE EMBRYO

To establish the subunit construction of elongation factor EF-1, interactions among four non-identical subunits of rice embryo EF-1 (alpha, beta, beta', and gamma) were analyzed with polyacrylamide gel electrophoresis. Complexes beta beta', alpha beta, alpha beta', and beta gamma were formed by mixing the two respective subunits. However, no complex was formed between EF-1 beta' and EF-1 gamma. Complexes containing three subunits like alpha beta beta', alpha beta gamma, and beta beta'gamma, were formed by mixing the three respective subunits. EF-1 was reconstructed when each subunit was added in the following order, beta, beta', gamma, and alpha. The affinity of EF-1 alpha for other subunits was as follows, beta beta'gamma > beta beta' > beta divided by beta'. Likewise, the affinity of EF-1 gamma for other subunits was: beta beta'gamma > beta >> beta'. Phe-tRNA binding activity of the reconstructed EF-1 was about 90% of that of the native EF-1. From these results, we concluded that rice embryo EF-1 is constructed of equimolar amount of four subunits, alpha, beta, beta' and gamma.