Proofreading activities of leucyl-tRNA synthetase prevent noncanonical mistranslation of the Escherichia coli proteome

Cvetešić, Nevena (2015) Proofreading activities of leucyl-tRNA synthetase prevent noncanonical mistranslation of the Escherichia coli proteome. Doctoral thesis, Faculty of Science > Department of Chemistry.

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Abstract

Aminoacyl-tRNA synthetases (aaRS) are enzymes that catalyse pairing of amino acids and tRNAs. As coupling of cognate pairs is crucial for accurate protein biosynthesis, aaRSs have developed complex proofreading mechanisms for correction of errors made in amino acid selection. Proofreading may occur before (hydrolysis of aminoacyl-adenylate), or after transfer of amino acid to tRNA (hydrolysis of misacylated tRNA). Synthetic and hydrolytic reactions of leucyl-tRNA synthetase (LeuRS) are characterised in detail within this thesis. The results demonstrate that LeuRS lacks tRNA-dependent pre-transfer editing and relies on robust post-transfer editing to clear aminoacylation errors. Isoleucine is generally thought to be a significant threat for accurate leucylation. However, kinetic experiments demonstrate that LeuRS efficiently excludes isoleucine in the synthetic reaction and that hydrolytic repair does not have a role in isoleucine elimination. A recent study showed that norvaline, a non-proteinogenic amino acid, accumulates in bacterial cytoplasm during oxygen deprivation. It appears that the major biological role of LeuRS editing is exclusion of norvaline from the genetic code. Research within this thesis reveals that LeuRS editing is interconnected with cellular mechanisms that ensure bacterial adaptability to low-oxygen environment.

Item Type: Thesis (Doctoral thesis)
Keywords: elongation factor Tu, leucyl-tRNA synthetase, micro-aerobic conditions, mistranslation, norvaline, proofreading
Supervisor: Gruić Sovulj, Ita
Date: 2015
Number of Pages: 161
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Faculty of Science > Department of Chemistry
Depositing User: Branka Maravic
Date Deposited: 31 Mar 2015 12:29
Last Modified: 12 Feb 2016 13:46
URI: http://digre.pmf.unizg.hr/id/eprint/3749

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