https://mmbr.asm.org/content/mmbr/36/4/525.full.pdf

Pedigrees of some mutant strains of Escherichia coli K-12.

A rapid, sensitive method is described for measuring C14-aminoacyl-sRNA interactions with ribosomes which are specifically induced by the appropriate RNA codewords prior to peptide-bond formation. Properties of the codeword recognition process and the minimum oligonucleotide chain length required to induce such interactions are presented. The trinucleotides, pUpUpU, pApApA, and pCpCpC, but not dinucleotides, specifically direct the binding to ribosomes of phenylalanine-, lysine-, and proline-sRNA, respectively. Since 59-terminal, 39-terminal, and internal codewords differ in chemical structure, three corresponding classes of codewords are proposed. The recognition of each class in this system is described. The template efficiency of trinucleotide codewords is modified greatly by terminal phosphate. Triplets with 59-terminal phosphate are more active as templates than triplets without terminal phosphate. Triplets with 39- or 39 (29)-terminal phosphate are markedly less active as templates. These findings are discussed in relation to the probable functions of terminal codewords. The modification of RNA and DNA codewords, converting sense into missense or nonsense codewords, is suggested as a possible regulatory mechanism in protein synthesis.

https://science.sciencemag.org/content/sci/145/3639/1399.full.pdf

Rna codewords and protein synthesis. the effect of trinucleotides upon the binding of srna to ribosomes.

Although chemists can synthesize virtually any small organic molecule, our ability to rationally manipulate the structures of proteins is quite limited, despite their involvement in virtually every life process. For most proteins, modifications are largely restricted to substitutions among the common 20 amino acids. Herein we describe recent advances that make it possible to add new building blocks to the genetic codes of both prokaryotic and eukaryotic organisms. Over 30 novel amino acids have been genetically encoded in response to unique triplet and quadruplet codons including fluorescent, photoreactive, and redox-active amino acids, glycosylated amino acids, and amino acids with keto, azido, acetylenic, and heavy-atom-containing side chains. By removing the limitations imposed by the existing 20 amino acid code, it should be possible to generate proteins and perhaps entire organisms with new or enhanced properties.

Expanding the genetic code.

Derivations and genotypes of some mutant derivatives of Escherichia coli K12

The release of enzymes by osmotic shock from Escherichia coli in exponential phase.

I Yanofsky, C., and P. St. Lawrence, Ann. Rev. Microbiol., 14, 311 (1960). 16 Yanofsky, C., D. R. Helinski, and B. Maling, in Cellular Regulatory Mechanisms, Cold Spring Harbor Symposia on Quantitative Biology, vol. 26 (1961), p. 11. 17 Hoagland, M. B., Brookhaven Symposia in Biol., 12, 40 (1959). 18 Crick, F. H. C., "The Biological Replication of Macromolecules," in Symposium Soc. Expt. Biol., 12, 138 (1958). 19 Chapeville, F., F. Lipmann, G. von Ehrenstein, B. Weisblum, W. Ray, and S. Benzer, these PROCEEDINGS, 48, 1086 (1962). 20 von Ehrenstein, G., and F. Lipmann, these PROCEEDINGS, 47, 941 (1961). 21 Nomura, M., and S. Benzer, J. Mol. Biol., 3, 684 (1961). 22 Bode, W., doctoral dissertation, University of Cologne (1962). 23 Weisblum, B., S. Benzer, and R. Holley, manuscript in preparation. 24 Benzer, S., and B. Weisblum, these PROCEEDINGS, 47, 1149 (1961).

https://www.pnas.org/content/pnas/48/7/1121.full.pdf

O. Siddiqi

Papers

Suppression of mutations in the alkaline phosphatase structural cistron of e. coli