Naslov
Translational quality control mechanisms that eliminate the non-canonical norvaline from the genetic code in Escherichia coli

Autori
Cvetešić, Nevena ; Biluš, Mirna ; Dulić, Morana ; Gruić-Sovulj, Ita

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

Izvornik
ESF-EMBO Symposium ; Bacterial Networks (Bacnet 15) / Victor Sourjik and Julia Vorholt - Sant Feliu de Guíxols : ESF-EMBO, 2015, 98-100

Skup
Bacterial Networks (Bacnet 15)

Mjesto i datum
Sant Feliu de Guíxols, Španjolska, 09.05.2015. - 14.05.2015

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
editing; leucyl-tRNA synthetase; norvaline; non-canonical mistranslation

Sažetak
Aminoacyl-tRNA synthetases (aaRS) catalyze ATP- dependent covalent coupling of cognate amino acids and tRNAs for ribosomal protein synthesis. Cellular requirements for accurate aminoacylation are high because this reaction defines the genetic code. Yet, some aaRSs are incapable to discriminate against structurally similar amino acids solely during the binding or chemical steps. These enzymes evolved editing mechanisms to keep error in aminoacyl- tRNA synthesis low. Both, the non-cognate aminoacyl-AMP intermediate and the non-cognate final product, misaminoacylated tRNA, can be cleared by the intrinsic aaRS hydrolytic activities. It was generally assumed that editing mechanisms in aaRSs exist to prevent errors in protein synthesis that originate from substitutions with the structurally similar canonical amino acids. Yet, we and others recently pointed out that aaRS editing may also act as a fortress of the canonical translation. We unveiled that a major threat for accurate decoding of leucine codons in Escherichia coli is the non-canonical norvaline rather than the anticipated canonical isoleucine[1]. Norvaline is a side-product of the leucine biosynthetic pathway that may accumulate to milimolar concentration in E. coli under microaerobic growth [2]. It may compete with incorporation of both leucine and isoleucine into proteins because leucyl- and isoleucly-tRNA synthetases (LeuRS and IleRS, respectively) discriminate against norvaline by only a 100-fold specificity exercised at ground-state binding alone. However, a threshold level of translational accuracy is ensured by rapid deacylation of the transiently formed Nva- tRNAIle and Nva-tRNALeu at the corresponding IleRS and LeuRS domains dedicated to this activity. Opposite to LeuRS, IleRS editing capacity also serves to prevent canonical mistranslation of isoleucine with valine. Hence, construction of the E. coli strain incapable of IleRS editing will enable comparison of the cellular tolerance toward canonical and non-canonical mistranslation. Such experiments are underway in our laboratory. In vivo consequences of non-canonical mistranslation were tested using E. coli strain with a defunct LeuRS editing domain. We demonstrated norvaline incorporation into E. coli proteome and its high toxicity in the absence of LeuRS proofreading. A noticeable decrease in viability under microaerobic growth conditions shown for E. coli deprived of LeuRS editing, further exposed a cross-talk between translational quality control and bacterial adaptive response mechanisms to ensure viability under changing environments. [1] Cvetesic N, Palencia A, Halasz I, Cusack S, Gruic-Sovulj I. (2014) EMBO J. 33, 1639-53. [2] Soini J, Falschlehner C, Liedert C, Bernhardt J, Vuoristo J, Neubauer P. (2008) Microb Cell Fact. 21, 7:30.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Biologija

POVEZANOST RADA