title: Perspectives and Insights into the Competition for Aminoacyl-tRNAs between the Translational Machinery and for tRNA Dependent Non-Ribosomal Peptide Bond Formation.
abstract: Aminoacyl-tRNA protein transferases catalyze the transfer of amino acids from aminoacyl-tRNAs to polypeptide substrates. Different forms of these enzymes are found in the different kingdoms of life and have been identified to be central to a wide variety of cellular processes. L/F-transferase is the sole member of this class of enzyme found in Escherichia coli and catalyzes the transfer of leucine to the N-termini of proteins which result in the targeted degradation of the modified protein. Recent investigations on the tRNA specificity of L/F-transferase have revealed the unique recognition nucleotides for a preferred Leu-tRNA(Leu) isoacceptor substrate. In addition to discussing this tRNA selectivity by L/F-transferase, we present and discuss a hypothesis and its implications regarding the apparent competition for this aminoacyl-tRNA between L/F-transferase and the translational machinery. Our discussion reveals a hypothetical involvement of the bacterial stringent response that occurs upon amino acid limitation as a potential cellular event that may reduce this competition and provide the opportunity for L/F-transferase to readily increase its access to the pool of aminoacylated tRNA substrates.
authors.affiliation: Department of Biochemistry, Faculty of Medicine &amp; Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada. awfung@ualberta.ca.|Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A1, Canada. awfung@ualberta.ca.
authors.forename: Angela W S
authors.initials: AW
authors.lastname: Fung
authors.affiliation: Department of Biochemistry, Faculty of Medicine &amp; Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada. payoe@ualberta.ca.|Institute of Technology, Faculty of Science and Technology, University of Tartu, Noorse St 1, Tartu 50411, Estonia. payoe@ualberta.ca.
authors.forename: Roshani
authors.initials: R
authors.lastname: Payoe
authors.affiliation: Department of Biochemistry, Faculty of Medicine &amp; Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada. rfahlman@ualberta.ca.|Department of Oncology, Faculty of Medicine &amp; Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada. rfahlman@ualberta.ca.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Fahlman
keywords: (p)ppGpp; EF-Tu; L/F-transferase; N-end rule; aminoacyl-tRNA; stringent response; tRNA