Protein Biosynthesis: The Codon‐Specific Activation of Amino Acids

Abstract

At the start of protein biosynthesis the amino acids are chemically activated by esterification with transfer ribonucleic acids bearing the appropriate anticodons. The esterification is catalyzed with an exceptionally high specificity by aminoacyl-tRNA synthetases. Current knowledge of the structural properties of the reactants, the course of the reaction, and the reasons for its specificity are summarized.

Synthetic, structural and biological studies of the ubiquitin system: the total chemical synthesis of ubiquitin

“…Residue numbers are given in parentheses. Peptide sequence TO Tl T2 T3 T4 T5 T6 T7 T8 T9 T10 Ala-Lys (28)(29) lle-Gln-Asp-Lys (30-33) Leu-Arg-Gly-Gly (73-76) Thr-Leu-Thr-Gly-Lys (7-11) Gln-Leu-Glu-Asp-Gly-Arg (49-54) Glu-Gly-lle-Pro-Pro-Gln-Gln-Arg (34-42) Thr-Leu-Ser-Asp-Tyr-Asn-lle-Gln-Lys (55-63) Leu-lle-Phe-Ala-Gly-Lys (43-48) Met-Gln-Ile-Phe-Val-Lys (1)(2)(3)(4)(5)(6) Glu-Ser-Thr-Leu-His-Leu-Val-Leu-Arg (64-72) Thr-lle-Thr-Leu-Glu-Val-Glu-Pro-Ser-Asp-Thr-lle-Glu-Asn-Val-Lys (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) lysozyme by the El enzyme, native and synthetic ubiquitin exhibited identical activities (M. P. Mee, J. E. Arnold and J. Mayer, personal communication).…”

“…At present, many gene-based studies lead to small quantities of protein, although this can be enhanced by overexpression to give proteins containing a-amino acids for which there is tRNA. The recent use [1,2] of redundant stop codons in RNA for loading of unnatural a-amino acids offers exciting opportunities but, at present, it has some limitations in the scale of protein produced.…”

Phenylalanyl-tRNA synthetase of Escherichia coli K 10. Multiple enzyme.cntdot.aminoacyl-tRNA complexes as a consequence of substrate specificity

“…If so, aminoacyl-tRNA synthetases could not be enzymatically active, because they would be blocked with the aminoacyl-tRNA. Not unexpectedly, measurements have revealed dissociation constants of the enzyme-aminoacyl-tRNA complexes that are far from those calculated and that are of the same magnitude as the dissociation constants for the substrate tRNAs (Holler, 1976; Jacques & Blanquet, 1977).…”

“…At equilibrium, this complex is present at a fourfold higher -A.minoacyl-tRNA synthetases are highly specific with respect to the esterification of a genetically related amino acid and tRNA. One of several mechanisms which accounts for the specificity (Holler, 1978) is the association of the synthetase with the correct amino acid and tRNA. The formation of complexes is selective because of the strong binding forces between a synthetase and the correct amino acid and tRNA, respectively.…”

“…The formation of complexes is selective because of the strong binding forces between a synthetase and the correct amino acid and tRNA, respectively. At first glance, this elegant way to accomplish specificity creates the problem that the fragments joined together in the aminoacyl-tRNA are predicted on the basis of free-energy calculations to give rise to an impractically high stability of the enzyme-product complex (Holler, 1978).…”