Open AccesstRNA‐dependent amino acid discrimination by yeast seryl‐tRNA synthetase
Author(s) -
GruicSovulj Ita,
Landeka Irena,
Söll Dieter,
WeygandDurasevic Ivana
Publication year - 2002
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2002.03241.x
Subject(s) - transfer rna , amino acid , biochemistry , amino acyl trna synthetases , aminoacyl trna synthetase , enzyme , serine , saccharomyces cerevisiae , yeast , binding site , biology , threonine , genetic code , chemistry , stereochemistry , rna , gene
The ability of aminoacyl‐tRNA synthetases to distinguish between similar amino acids is crucial for accurate translation of the genetic code. Saccharomyces cerevisiae seryl‐tRNA synthetase (SerRS) employs tRNA‐dependent recognition of its cognate amino acid serine [Lenhard, B., Filipic, S., Landeka, I., Skrtic, I., Söll, D. & Weygand‐Durasevic, I. (1997) J. Biol. Chem. 272 , 1136–1141]. Here we show that dimeric SerRS enzyme complexed with one molecule of tRNA Ser is more specific and more efficient in catalyzing seryl‐adenylate formation than the apoenzyme alone. Sequence‐specific tRNA–protein interactions enhance discrimination of the amino acid substrate by yeast SerRS and diminish the misactivation of the structurally similar noncognate threonine. This may proceed via a tRNA‐induced conformational change in the enzyme's active site. The 3′‐terminal adenosine of tRNA Ser is not important in effecting the rearrangement of the serine binding site. Our results do not provide an indication for a readjustment of ATP binding in a tRNA‐assisted manner. The stoichiometric analyses of the complexes between the enzyme and tRNA Ser revealed that two cognate tRNA molecules can be bound to dimeric SerRS, however, with very different affinities.