Molecular cloning of recombinant DNA : proceedings of the Miami winter symposia, January 1977 / edited by W.A. Scott, R. Werner ; sponsored by the Department of Biochemistry, University of Miami, School of Medicine, Miami, Florida.

Date:
1977
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Molecular cloning of recombinant DNA : proceedings of the Miami winter symposia, January 1977 / edited by W.A. Scott, R. Werner ; sponsored by the Department of Biochemistry, University of Miami, School of Medicine, Miami, Florida. Source: Wellcome Collection.

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    8 PAUL BERG ably more unstable than acetyl phosphate but it was quite straight forward to show that it yielded ATP in the presence of PPi and acetyl CoA with CoA (11). Additional experiments proved that the Lipmann-Lynen model was incorrect and sup¬ ported my formulation of the reaction (Fig. 2). Once again experiments with an impure enzyme had given misleading information about its mechanism; in this case the most likely impurities in the епгзппе preparation were free acetate and AMP. When I first reported these findings in 1955 at the ASBC meetings in San Francisco I was quite appre¬ hensive about how they would be received by Lipmann and Lynen. But my apprehension was unfounded because Fritz Lipmann was most generous in his praise of my work and genuinely delighted at the novelty of the mechanism of the reaction. Years later, when I first met Fitzie Lynen, he was equally complementary. It was, indeed, one of the exciting chapters of my scientific career. I shall always be grateful to Romberg for his sup¬ port and encouragement during that work and for insisting that I publish the work independently. Becoming a Molecular Biologist During the search for the hypothetical adenyl-enz3mie com¬ pound in other cell extracts, I discovered other ATP-PPj^ exchange activities. Of particular interest was the finding that amino acids promoted an ATP-PP^ exchange. It seemed reasonable, by analogy, with the aceto-CoA kinase reaction, that this occurred via the formation of aminoacyl adenylates (the first reaction in Fig. 3), an assumption which proved to be correct. This was established when I purified an епгзппе that catalyzed the formation of L-methionyl adenylate using ATP and L-methionine as well as the formation of ATP from synthetic methionyl adenylate and PP¿ (12). Jim Ofengand, my first graduate student, and I reasoned that there must be a natural aminoacyl acceptor analogous to CoA and V7e set out to find the hypothetical acceptor. I thought it might be the template for protein synthesis, but the acceptor turned out to be small polynucleotides subsequently named tRNAs. (13) (The second reaction in Fig. 3). The elegant work of Mahlon Hoagland and Paul Zamecnik (14) established that tRNAs were, in fact, the adaptors Crick foresaw (15) would be needed to translate the genetic code words for protein synthesis. Our subsequent work established that separate, specific enzymes (aminoacyl tRNA synthetases) catalyzed the attachment of each amino acid to one or a few cognate tRNA chains (see reaction 3 in Fig. 3) (16).