Pregledni rad
The Accuracy of Seryl-tRNA Synthesis
Ivana Weygand-Durasevic
; Rudjer Bošković Institute, 10000 Zagreb, Croatia
Ita Gruic-Sovulj
; Department of Chemistry, Faculty of Science, University of Zagreb, HR-10000 Zagreb, Croatia
Sanda Rocak
; Rudjer Bošković Institute, 10000 Zagreb, Croatia
Irena Landeka
; Department of Chemistry, Faculty of Science, University of Zagreb, HR-10000 Zagreb, Croatia
Sažetak
The high level of translational fidelity 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 (aaRS), i.e. their ability to choose among competing structurally similar substrates. Our studies have revealed that accurate seryl-tRNA synthesis in yeast and plants is accomplished via tRNA-assisted optimization of amino acid binding to the active site of seryl-tRNA synthetase (SerRS). 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’s active site. The influence of tRNASer, on the activation of serine by SerRS variants mutated in the active site, is much less pronounced. Although SerRS misactivates structurally similar threonine in vitro, the formation of such erroneous threonyl-adenylate is reduced in the presence of nonchargeable tRNASer analog. Thus, the sequence-specific tRNA : SerRS interactions enhance the accuracy of amino acid recognition. Another type of quality control mechanism in tRNA serylation is assumed to be based on the complex formation between SerRS and a nonsynthetase protein. Using in vivo interaction screen, yeast peroxin Pex21p was identified as SerRS interacting protein. This was confirmed by an in vitro binding assay. Kinetic experiments performed in the presence of Pex21p revealed that this peroxin acts as an activator of seryl-tRNA synthetase in the aminoacylation reaction.
Ključne riječi
aminoacyl-tRNA synthetase; tRNA-dependent amino acid recognition; amino acid selection; protein-protein interactions; activation of aminoacylation
Hrčak ID:
178514
URI
Datum izdavanja:
12.12.2002.
Posjeta: 681 *