Misactivated amino acids translocate at similar rates across surface of a tRNA synthetase

AUTOR(ES)

Nomanbhoy, Tyzoon K.

FONTE

The National Academy of Sciences

RESUMO

Certain aminoacyl-tRNA synthetases have a second active site that destroys (by hydrolysis) errors of amino acid activation. For example, isoleucyl-tRNA synthetase misactivates valine (to produce valyl adenylate or Val-tRNAIle) at its active site. The misactivated amino acid is then translocated to an editing site located >25 Å away. The role of the misactivated amino acid in determining the rate of translocation is not known. Valyl-tRNA synthetase, a close homolog of isoleucyl-tRNA synthetase, misactivates threonine, α-aminobutyrate, and cysteine. In this paper, we use a recently developed fluorescence-energy-transfer assay to study translocation of misactivated threonine, α-aminobutyrate, and cysteine. Although their rates of misactivation are clearly distinct, their rates of translocation are similar. Thus, the rate of translocation is independent of the nature of the misactivated amino acid. This result suggests that the misactivated amino acid per se has little or no role in directing translocation.

Documentos Relacionados

• Blocking site-to-site translocation of a misactivated amino acid by mutation of a class I tRNA synthetase
• Interstice mutations that block site-to-site translocation of a misactivated amino acid bound to a class I tRNA synthetase
• Expanding tRNA recognition of a tRNA synthetase by a single amino acid change
• Engineering a tRNA and aminoacyl-tRNA synthetase for the site-specific incorporation of unnatural amino acids into proteins in vivo
• Identification of Amino Acids in the N-terminal Domain of Atypical Methanogenic-type Seryl-tRNA Synthetase Critical for tRNA Recognition*