Synthesis and repair of 3'-end of tRNA molecule by tRNA nucleotidyltransferase

Hajdinjak, Mateja (2010) Synthesis and repair of 3'-end of tRNA molecule by tRNA nucleotidyltransferase. Bachelor's thesis, Faculty of Science > Department of Biology.

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Abstract

ATP(CTP):tRNA nucleotidyltransferase (CCA enzyme) is responsible for posstranscriptional synthesis and repair of the 3'-terminal CCA sequence in tRNA trascripts, which is indispensable in translation reactions and therefore of vital importance for the cell. CCA enzyme differs from standard DNA and RNA polymerases in several ways. Apart from the fact that it does not require a nucleic acid template, it incorporates only restricted number of nucleotides in a tRNA primer and then stops reaction at a high efficiency and accuracy. It also selects exclusively CTP and ATP for incorporation and it is highly selective for tRNAlike structures as a polymerization substrate. Because of the existance of single active site, this active site has to change the specificity between ATP i CTP depending on cellular concentrations of nucleotides and the sequence of the tRNA 3' end. CCA enzymes evolved in two classes during evolution, and although this two classes share an overall structural organization and fulfill indentical functions, the individual domains vary extremely and have different mechanistic solutions. Class 1 enzymes are found only in archaea while class2 enzymes are found in bacteria and eukaryotes. Both classes of CCA enzymes have a highly conserved catalytic core within the head domain having three carboxylates in a geometry similar to those of template-dependent DNA and RNA polymerases that use two metal ion mechanism for phosphoryl transfer. Both classes use Mn2+ and Mg2+ as productive metal ions. Except for the differences between two classes, even closely related enzymes that belong to the same class differ substantially.

Item Type: Thesis (Bachelor's thesis)
Supervisor: Gruić Sovulj, Ita
Date: 2010
Number of Pages: 20
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 29 Oct 2014 10:35
Last Modified: 29 Oct 2014 10:35
URI: http://digre.pmf.unizg.hr/id/eprint/3214

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