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Journal of Bacteriology, December 2008, p. 7754-7761, Vol. 190, No. 23
0021-9193/08/$08.00+0     doi:10.1128/JB.00984-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Mutations in Conserved Helix 69 of 23S rRNA of Thermus thermophilus That Affect Capreomycin Resistance but Not Posttranscriptional Modifications

Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island 02912,¹ Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense M, Denmark,² Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, Nakornpathom 73170, Thailand³

Received 16 July 2008/ Accepted 11 September 2008

Translocation during the elongation phase of protein synthesis involves the relative movement of the 30S and 50S ribosomal subunits. This movement is the target of tuberactinomycin antibiotics. Here, we describe the isolation and characterization of mutants of Thermus thermophilus selected for resistance to the tuberactinomycin antibiotic capreomycin. Two base substitutions, A1913U and mU1915G, and a single base deletion, mU1915, were identified in helix 69 of 23S rRNA, a structural element that forms part of an interribosomal subunit bridge with the decoding center of 16S rRNA, the site of previously reported capreomycin resistance base substitutions. Capreomycin resistance in other bacteria has been shown to result from inactivation of the TlyA methyltransferase which 2'-O methylates C1920 of 23S rRNA. Inactivation of the tlyA gene in T. thermophilus does not affect its sensitivity to capreomycin. Finally, none of the mutations in helix 69 interferes with methylation at C1920 or with pseudouridylation at positions 1911 and 1917. We conclude that the resistance phenotype is a consequence of structural changes introduced by the mutations.

Published ahead of print on 19 September 2008.