Poster abstracts

Poster number 47 submitted by Daoming Qin

Characterization of 16S rRNA mutations that decrease the fidelity of translation initiation

Daoming Qin (The Ohio State Biochemistry Program, The Ohio State University), Nimo M. Abdi (Department of Microbiology, The Ohio State University), Kurt Fredrick (The Ohio State Biochemistry Program, Department of Microbiology, The Ohio State University)

Abstract:
In bacteria, initiation of translation is kinetically controlled by factors IF1, IF2, and IF3, which work in conjunction with the 30S subunit to ensure accurate selection of the initiator tRNA (fMet-tRNAfMet) and the start codon. Here, we show that mutations G1338A and A790G of 16S rRNA decrease initiation fidelity in vivo and do so in distinct ways. Mutation G1338A increases the affinity of tRNAfMet for the 30S subunit, suggesting that G1338 normally forms a suboptimal Type II interaction with fMet-tRNAfMet. By stabilizing fMet-tRNAfMet in the pre-initiation complex, G1338A may partially compensate for mismatches in the codon-anticodon helix and thereby increase spurious initiation. Unlike G1338A, A790G decreases the affinity of IF3 for the 30S subunit. Thus A790G may indirectly stabilize fMet-tRNAfMet in the pre-initiation complex and/or promote premature docking of the 50S subunit, resulting in increased levels of spurious initiation.

Keywords: ribosome, 16S rRNA, P site