Sinteza i popravak 3'-kraja molekule tRNA pomoću tRNA-nukleotidil-transferaze

undergraduate thesis

• Title (english): Synthesis and repair of 3'-end of tRNA molecule by tRNA nucleotidyltransferase
• Author: Mateja Hajdinjak
• Mentor: Ita Gruić-Sovulj (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2010, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Enzim ATP(CTP):tRNA-nukleotidil-transferaza (CCA enzim) katalizira posttranskripcijsku sintezu i popravak slijeda CCA na 3'-kraju molekule tRNA, neophodnog u reakcijama translacije i stoga od životne važnosti za stanicu. CCA enzim se razlikuje od standardnih DNA- i RNA-polimeraza u nekoliko karakteristika. Osim što ne treba nukleinsku kiselinu kao kalup, u molekulu tRNA koja služi kao klica ugrađuje strogo određen broj nukleotida, zaustavljajući reakciju visokom efikasnošću i točnošću. Također, CCA enzim za ugradnju odabire isključivo CTP i ATP i jako je selektivan prema strukturama nalik molekuli tRNA kao polimerizacijskim supstratima. Zbog prisutnosti samo jednog aktivnog mjesta, ono mora promijeniti specifičnost ugradnje između ATP-a i CTP-a, ovisno o staničnoj koncentraciji nukleotida i slijedu na 3'-kraju molekule tRNA. Tijekom evolucije došlo je do razvoja dvaju razreda CCA enzima koji se, iako dijele sveukupnu strukturnu organizaciju i obavljaju identične funkcije, izrazito razlikuju u strukturi pojedinačnih domena i posjeduju drugačija mehanistička rješenja. Enzimi razreda 1 prisutni su samo u arhejama, dok su enzimi razreda 2 prisutni u bakterijama i eukariotima. Oba razreda CCA enzima sadrže visoko očuvanu katalitičku srž u domeni glave s tri karboksilata u rasporedu karakterističnom za DNA- i RNA-polimeraze koje koriste mehanizam dvaju metalnih iona za prijenos fosforila. Oba razreda enzima ovise o metalnim ionima, pri čemu primarno koriste Mg2+ i Mn2+ kao produktivne metalne ione. Osim razlike između dvaju razreda enzima, postoje značajne razlike između enzima koji pripadaju istom razredu, što je vidljivo na primjeru ljudskog i CCA enzima iz bakterije E. coli.

Abstract (english)

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.

• Keywords: 3'-kraj molekule tRNA; tRNA-nukleotidil-transferaza
• Keywords (english): 3'-end of tRNA molecule; tRNA nucleotidyltransferase
• Language: croatian
• URN:NBN: urn:nbn:hr:217:256173
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-03-23 11:51:57