Chicken liver transfer ribonucleic acid: heterologous interaction of alanine transfer ribonucleic acid with yeast.

We are attempting to determine the nature of specific RNA-protein interactions by study of tRNA charging by homologous and heterologous enzymes. tRNAklatRNARNA3 t were prepared by phenoxyacetylation of alanyl-tRNA and separation on benzoylated DEAE-cellulose (Gillam, Blew, Warrington, von Tigerstrom & Tener, 1968). A partially purified alanyl-tRNA synthetase from yeast forms alanyl-tRNAAla tandalanyl-tRNAAllacke. yeast chice equally well. In contrast, a similar alanyl-tRNA synthetase from chicken liver forms the heterologous alanyl-tRNAyeast less easily than the homologous alanyl-tRNA Ahla A comparison of the kinetics of charging the two species of RNA, by using a partially purified alanyl-tRNA synthetase from chicken liver, showed that the heterologous system has aKm for tRNAAlaat that is ten to 20 times larger, and a Vmax. three to four times smaller, than is found for the homologous tRNAAhCla These results are supported by the fact that a large excess of yeast tRNA will inhibit the rate at which the chicken enzyme will form alanyl-tRNA with smaller amounts of chicken tRNA. Preliminary results on the binding of phenoxyacetylalanyl-tRNA preparations to chicken liver enzyme indicate that the heterologous adduct is kinetically more stable than the homologous one at neutral pH. Thus it seems that with the heterologousRNAthe rates of association and dissociation are both decreased.