Macromolecular complexes of aminoacyl-tRNA synthetases and their role in translational quality control and non-ribosomal peptide synthesis
Makromolekularni kompleksi aminoacil-tRNA-sintetaza i njihova uloga u kontroli ribosomske i neribosomske biosinteze proteina
Trajanje / Duration:
01. 12. 2007. - 30. 11. 2010.
Voditelj projekta / Project leader:
Su-voditelj projekta / Project co-leader:
Dr. sc. Nenad Ban, prof. (ETH Zürich, Švicarska)
Financiranje / Funding:
Ustanova - nositelj projekta / Administering institution:
Partnerske ustanove / Partner institutions:
PLIVA Croatia Ltd. / Hospira d. o. o.
Aminoacil-tRNA-sintetaze (aaRS) su enzimi potrebni za biosintezu proteina u svim živim organizmima. Kataliziraju povezivanje transfer-RNA s njihovim pripadnim aminokiselinama, koje se potom polimeriziraju na ribosomima. Nova su istraživanja pokazala da se specifičnost i djelotvornost ovih enzima mijenja pri interakciji s drugim staničnim proteinima. Glavni ciljevi projekta su: i) razjasniti način formiranja i ulogu makromolekularnih kompleksa seril-tRNA-sintetaza pri ribosomskoj biosintezi proteina; ii) ispitati eventualno učešće seril-tRNA-sintetaza i/ili njima srodnih enzma u neribosomskoj sintezi peptida. Istražiivanja se provode kombinacijom biokemijskih i kristalografskih metoda. Od potencijalnog su farmakološkog značaja, jer se neke sintetaze mogu učinkovito i specifično inhibirati, te su zanimljive mete za djelovanje antibiotika, a neke pak sudjeluju u neribosomskoj sintezi različitih prirodnih produkata.
Aminoacyl-tRNA synthetases (aaRS) are key enzymes in translation of genetic message, which catalyze esterification of transfer RNAs with their cognate amino acids. The synthetases are highly specific, but errors in amino acid and tRNA selection are occasionaly made and they interfere with accurate protein synthesis. The fidelity of protein synthesis is maintained by editing activities of synthetases, which remove noncognate amino acids from tRNAs before they are delivered to the ribosome. In some cases editing activity is provided by the association of synthetases with freestanding trans-acting proteins. Alternatively, formation of aaRS-macromolecular complexes, either with cognate tRNA or auxiliary noncatalytic proteins, can improve the quality of aminoacyl-tRNA synthesis by enhancing the selectivity of aaRS. The objective of this proposal is to study the role of macromolecular complexes of aaRSs in translational quality control. We will focus primarily on seryl-tRNA synthetases (SerRS). SerRS is phylogenetically intersting because there are two distinct serine-charging enzymes; a standard or bacterial-type SerRS found in the majority of organisms (prokaryotes, eukaryotes and archaea), and a highly diverged SerRS confined to the methanogenic archaea. We have previously shown that the accuracy and the efficiency of yeast SerRS is affected by complex formation with cognate tRNA, that enhances amino acid discrimination, and with a nonsynthetase protein, peroxin Pex21p, which stimulates the binding of cognate tRNA. The C-terminal extension, conserved in eukaryotic SerRSs, is absolutely required for maintaining the interaction between the two proteins. Further structural and biochemical studies are needed to elucidate the role of these complexes in translation and possibly in other cellular processes. Due to much higher occurrence of aaRSs macromolecular assemblies in higher eukaryotes, plant SerRSs will be addressed. Additionally, since both the structures and serylation mechanisms of methanogenic-type SerRSs are substantially different from those of bacterial-type counterparts, we will explore macromolecular associations of atypical methanogenic-type SerRSs. Although SerRS enzymes lack separate editing domains, some members of this family are capable of hydrolyzing non-cognate adenylates and may need aminoacylable tRNA as a cofactor. By using a series of structural tRNA variants, we will study the mechanism of tRNA-mediated editing in the confines of the synthetic site. Finally, our recent finding that some proteobacterial genomes comprise duplicated SerRS-like genes, raised our interest toward structural and functional characterization of these putative SerRS paralogs, which may be required for serine activation in non-ribosomal peptide synthesis. The research on both aminoacyl-tRNA synthetases and their paralogs has a potential for developing novel antibiotics.
Suradnici / Collaborators:
Dr. sc. Silvija Bilokapić (PMF)
Dr. sc. Sonja Lesjak (PMF)
Dr. sc. Marko Močibob (PMF)
Dr. sc. Ana Crnković (PMF)
Dr. sc. Marija Luić, znanst. savjetnica (IRB)
Nives Ivić, dipl. ing. / prof. biol. kem. (IRB)
Dr. sc. Michael Ibba, Assc. Prof. (OSU)
Dr. sc. Tina (Čepo) Kusalić (PLIVA / Hospira d. o. o.)
Ivan Paškvan, dipl. ing. (PLIVA / Hospira d. o. o.)