Sep 21, 2000

Amino acid selectivity in the aminoacylation of coenzyme A and RNA minihelices by aminoacyl-tRNA synthetases

The Journal of Biological Chemistry
H Jakubowski


Coenzyme A (CoA-SH), a cofactor in carboxyl group activation reactions, carries out a function in nonribosomal peptide synthesis that is analogous to the function of tRNA in ribosomal protein synthesis. The amino acid selectivity in the synthesis of aminoacyl-thioesters by nonribosomal peptide synthetases is relaxed, whereas the amino acid selectivity in the synthesis of aminoacyl-tRNA by aminoacyl-tRNA synthetases is restricted. Here I show that isoleucyl-tRNA synthetase aminoacylates CoA-SH with valine, leucine, threonine, alanine, and serine in addition to isoleucine. Valyl-tRNA synthetase catalyzes aminoacylations of CoA-SH with valine, threonine, alanine, serine, and isoleucine. Lysyl-tRNA synthetase aminoacylates CoA-SH with lysine, leucine, threonine, alanine, valine, and isoleucine. Thus, isoleucyl-, valyl-, and lysyl-tRNA synthetases behave as aminoacyl-S-CoA synthetases with relaxed amino acid selectivity. In contrast, RNA minihelices comprised of the acceptor-TpsiC helix of tRNA(Ile) or tRNA(Val) were aminoacylated by cognate synthetases selectively with isoleucine or valine, respectively. These and other data support a hypothesis that the present day aminoacyl-tRNA synthetases originated from ancestral forms that we...Continue Reading

  • References16
  • Citations12


Mentioned in this Paper

Alkalescens-Dispar Group
Valine-tRNA Ligase
Amino Acyl-tRNA Synthetases
Isoleucine-tRNA Ligase

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