Poster abstracts

Poster number 73 submitted by Robert Ross

Thermus thermophilus tRNAs-Asn, Asp, His and Tyr are not modified at the wobble position

Robert Ross (Department of Chemistry; University of Cincinnati), Kirk Gaston, Balasubrahmanyam Addepalli, Patrick Limbach (Department of Chemistry; University of Cincinnati)

Abstract:
Thermus thermophilus is a gram-negative thermophilic bacteria that has served as the model organism for recent studies into ribosome structure and function. Unlike a majority of bacteria, Thermus does not posses the hypermodified nucleoside queuosine (Q) within its tRNAs. In other bacteria, tRNAs coding for asparagine, aspartic acid, histidine and tyrosine contain Q, modified in place of guanosine, at position 34 – the wobble position. While the exact function of Q is still not understood, it appears that this modification may enhance translational fidelity through reading frame maintenance or improved decoding. Before undertaking a detailed study into the significance of queuosine’s absence in Thermus, we first sought to determine whether some other modified nucleoside is found at the wobble position of these four tRNAs. To answer this question, individual tRNAs from Thermus were purified using hybridization probes attached to biotinylated streptavidin beads. These purified tRNAs were digested with RNase A or T1 and the resulting oligonucleotides were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Mass spectrometry sequencing of the anticodon region of these four tRNAs reveals each to contain the genome-encoded guanosine, with no evidence that other modifications are found in place of queuosine for Thermus tRNAs. In addition to presenting the data characterizing the anticodon sequences for these four tRNAs, additional sequence information from each will be presented, including placement of modified nucleosides found at other sequence locations.

Keywords: Thermus Thermophilus, tRNA, queuosine