Naslov
Class I aaRS quality control mechanisms preserve canonical translation in Escherichia coli

Autori
Cvetešić, Nevena ; Biluš, Mirna ; Palencia, Andres ; Dulić, Morana ; Cusack, Stephen ; Gruić-Sovulj, Ita ;

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

Izvornik
25th tRNA Conference 2014 Abstract Book / Drainas, Denis ; Stathopoulos Constantinos - , 2014, 63-63

Skup
25th tRNA Conference 2014

Mjesto i datum
Kyllíni, Grčka, 21.09.2014. - 25.09.2014

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
leucyl-tRNA synthetase; isoleucyl-tRNA synthetase; proofreading; isoleucine; norvaline

Sažetak
Norvaline, a side product of the leucine biosynthetic pathway, accumulates in Escherichia coli under downshift of oxygen to the concentration capable to jeopardize accuracy of Ile-tRNAIle and Leu-tRNALeu synthesis. Incorporation of this non-canonical amino acid into the cell proteome is however prevented by rapid post-transfer editing within the IleRS and LeuRS CP1-editing domains. IleRS, unlike LeuRS, proofreads norvaline also at the level of tRNA- dependent pre-transfer editing. Intriguingly, non- proteinogenic norvaline, not isoleucine, sets up the requirement for LeuRS editing. This conclusion follows from a reassessment of the LeuRS discriminatory power using isoleucine that was additionally purified from traces of cognate leucine. Indeed, opposite to the prevailing opinion, we demonstrate that LeuRS discriminates against isoleucine with specificity of better than 104-fold, and thus obviates need for post-transfer editing of Ile-tRNALeu. Kinetic, structural and thermodynamic approaches establish that both very weak ground state binding and the decreased rate of the chemical step contribute to isoleucine specificity. Both features clearly distinguish isoleucine from norvaline which exhibits only 102- fold specificity in the LeuRS synthetic reaction. The growth of an E. coli strain deprived of LeuRS post-transfer editing displays accordingly a high intolerance towards a surplus of norvaline, but not isoleucine, in the media. Likewise, editing- dependent cell viability correlates well with micro-aerobic but not normal growth conditions. It thus appears that class I aaRS editing plays an important role in the E. coli adaptive response to quickly changing oxygen environments by preserving canonical translation under these naturally error- prone conditions.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Biologija

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