engleski

Fidelity of decoding by aminoacyl-tRNA synthetases

Translation is the process by which the genetic information contained in mRNA is used to determine the sequential order of amino acids in a protein. The high level of translational fidelity in the cell is ensured by various types of quality control mechanisms, which are adapted to prevent or correct naturally occurring mistakes. Accurate aminoacyl-tRNA synthesis is mostly dependent on the specificity of the aminoacyl-tRNA synthetases, i.e. their ability to choose between competing structurally similar substrates. Our studies have revealed that accurate seryl-tRNA synthesis is accomplished via tRNA-assisted optimization of amino acid binding to the enzyme active site. Based on our recent kinetic data, a mechanism is proposed by which transient protein:RNA complex activates the cognate amino acid more efficiently and more specifically than the apoenzyme alone. This may proceed via a tRNA-induced conformational change in the enzyme&#8217 ; s active site. SerRS enzymes slightly misactivate structurally similar threonine, but the formation of erroneous threonyl-adenylate is reduced in the presence of tRNASerCC. Thus, the sequence-specific tRNA:SerRS interactions enhance the accuracy of amino acid recognition, making corrective mechanisms unnecessary. In addition, it seems that the quality of seryl-tRNA formation may be improved by the complex formation between SerRS and a nonsynthetase protein. Potential biological relevance of the interaction between yeast SeRS and peroxin Pex21p, which has been identified in yeast, will be discussed.

aminoacyl-tRNA synthetases; tRNA; accuracy of protein synthesis

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