Polypeptide Elongation Factors of the Developing Chick Brain

Abstract

The polypeptide elongation factors (EF‐1_L, EF‐1_H, 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‐1_H of the chick brain ranged from 5 to 10 × 10⁵, and was different from that of the chick liver (about 7 × 10⁵). The molecular weight of other purified factors was about 5 × 10⁴ for EF‐1_L. and 9.4 × 10⁴ 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‐1_L was a major component of EF‐1 in an early embryonic stage, while EF‐1_H became recognizable in the 3rd embryonic week. Moreover, the EF‐1_H 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‐1_L. It is proposed that the brain EF‐1_H could be due to aggregates consisting of EF‐1_L, a stimulatory factor, and other components.