IN VlTRO BINDING OF PHENYLALANYL-tRNA TO NEONATAL AND ADULT MOUSE BRAIN RIBOSOMES

The ability of brain ribosomes, isolated from mice of various ages, to bind phenylalanyl-tRNA was measured under various reaction conditions. In the presence of template RNA (polyuridylic acid) the binding could be measured by both enzymic and non-enzymic assays. In general, the binding requirements for the brain system were similar to those previously described for microbial and eukaryotic systems. Although previous studies have shown that ribosomes obtained from increasingly older mow brain tissue were less active in polyphenylalanine synthesis, no significant differences in phenylalanyl-tRNA binding to polysome complexes could be detected. The binding of phenylalanyl-tRNA by ribosomes isolated from both neonatal and mature mouse brain tissue was similar with regard to GTP and polyuridylic acid dependence, magnesium ion concentration and reaction kinetics. Similar binding of phenylalanyl-tRNA by young and mature brain ribosomes was also measured with ribonucleoprotein particles previously stripped with puromycin. The results are discussed in light of the rapid alteration of macromolecular synthesis during postnatal brain development and the possible role of the interaction between ribosomes and tRNA.