Polypeptide elongation factors of the developing chick brain.

The polypeptide elongation factors (EF-1L, EF-1H, and EF-2) of the developing chick brain were separated and purified by means of a combination of gel chromatographic methods. The molecular weight of EF-1H of the chick brain ranged from 5 to 10 x 10(5), and was different from that of the chick liver (about 7 x 10(5). The molecular weight of other purified factors was about 5 x 10(4) for EF-1L and 9.4 x 10(4) for EF-2. High activities of polyphenylalanine (poly-Phe) synthesis per mg protein in the developing chick brain were observed between the 3rd embryonic week and the 1st post-hatch week and declined afterwards. On the other hand, the levels of both EF-1 and EF-2 per mg protein in the brain were observed to be high in an early embryonic stage, gradually declining afterwards to the adult level. The brain EF-1L was a major component of EF-1 in an early embryonic stage, while EF-1H became recognizable in the 3rd embryonic week. Moreover, the EF-1H activities were found to be more than double with regard to the binding reaction and to be more than 10-fold as active in respect to poly-Phe synthesis in comparison with the activities of EF-1L. It is proposed that the brain EF-1H could be due to aggregates consisting of Ef-1L, a stimulatory factor, and other components.