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Breaking sieve for steric exclusion of a noncognate amino acid from active site of a tRNA synthetase

Swairjo, Manal A ; Schimmel, Paul R

Proceedings of the National Academy of Sciences of the United States of America, 25 January 2005, Vol.102(4), pp.988-93 [Rivista Peer Reviewed]

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  • Titolo:
    Breaking sieve for steric exclusion of a noncognate amino acid from active site of a tRNA synthetase
  • Autore: Swairjo, Manal A ; Schimmel, Paul R
  • Descrizione: The genetic code is fixed in aminoacylation reactions catalyzed by aminoacyl-tRNA synthetases. Amino acid discrimination occurs at two sites: one for amino acid activation and aminoacylation and one for editing misactivated amino acids. Although the active site sieves out bulkier amino acids, misactivation occurs with substrates whose side chains are smaller than the cognate one. Paradoxically, although alanyl-tRNA synthetase activates glycine as well as alanine, the sterically larger (than alanine) serine is also misactivated. Here, we report crystal structures of an active fragment of Aquifex aeolicus alanyl-tRNA synthetase complexed, separately, with Mg2+-ATP, alanine, glycine, and serine. Ala and Gly are bound in similar orientations in a side-chain-accommodating pocket, where alpha-amino and carboxyl groups are stabilized by salt bridges, and the carboxyl by an H-bond from the side chain NH2 of Asn-194. In contrast, whereas the same two salt bridges stabilize bound Ser, H-bonding of...
  • Fa parte di: Proceedings of the National Academy of Sciences of the United States of America, 25 January 2005, Vol.102(4), pp.988-93
  • Soggetti: Alanine-Trna Ligase -- Chemistry
  • Lingua: Inglese
  • Identificativo: ISSN: 0027-8424 ; PMID: 15657145 Version:1

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