Naslov
Diverse network of editing pathways ensure fidelity of aminoacyl-tRNA synthesis

Autori
Gruić-Sovulj, Ita

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
The secret life of biomolecules HDBMB / Kovarik, Zrinka ; Varljen, Jadranka - , 2010

Skup
10th Congress of the Croatian Society of Biochemistry and Molecular Biology with international participation

Mjesto i datum
Opatija, Hrvatska, 15.09.2010. - 18.09.2010

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
pre-transfer editing; isoleucyl-tRNA synthetase

Sažetak
Aminoacyl-tRNA synthetases (AARSs) join amino acids with their cognate tRNAs ensuring formation of aminoacyl-tRNAs for protein biosynthesis. Aminoacylation occurs in ATP-dependent two step reaction ; formation of aminoacyl-adenylate (AA-AMP) is followed by transfer of the amino acid to tRNA. Structural similarities among certain amino acids render some AARS unable to distinguish them in the synthetic reactions alone. Thus, to maintain error rates in protein biosynthesis within tolerable levels, AARSs have developed hydrolytic proofreading to correct initial errors in amino acid selection. Diverse network of editing pathways has been shown to exist (1). Hydrolysis of the noncognate AA-AMP in tRNA-dependent or tRNA-independent manner is known as “pre-transfer” editing. Enhanced dissociation of noncognate AA-AMP may also contribute to “pre-transfer” editing activity. If the noncognate amino acid is transferred to the 3’-end of tRNA, the misacylated tRNA is hydrolyzed by “post-transfer” editing shown to occur within the distant editing domain. The mechanisms of pre-transfer editing have been uncertain. To distinguish between three proposed models (1) we have developed a new approach using isoleucyl- (IleRS) and valyl-tRNA syntetases (ValRS) as model enzymes (2). We demonstrate that tRNA-dependent hydrolysis of noncognate Val-AMP by IleRS is largely insensitive to mutations in the editing domain of the enzyme. Measurements of the microscopic rate constants for amino acid transfer to tRNA further suggest that pre-transfer editing in IleRS is an enzyme-catalyzed activity residing in the synthetic active site. We propose that the balance between pre-transfer and post-transfer editing pathways is controlled by kinetic partitioning of the noncognate AA-AMP. Rate constants for hydrolysis and transfer of a noncognate intermediate are roughly equal in IleRS, while in ValRS transfer to tRNA is 200-fold faster than hydrolysis. In consequence, editing by ValRS occurs nearly exclusively by post-transfer hydrolysis in the editing domain, while in IleRS both pre- and post-transfer editing are important.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Biologija

POVEZANOST RADA