Methylation at position 32 of tRNA catalyzed by TrmJ alters oxidative stress response in Pseudomonas aeruginosa
Abstract
Bacteria respond to environmental stresses using a variety of signaling and gene expression pathways , with translational mechanisms being the least well understood. Here, we identified a tRNA methyl-transferase in Pseudomonas aeruginosa PA14, trmJ, which confers resistance to oxidative stress. Analysis of tRNA from a trmJ mutant revealed that TrmJ catalyzes formation of Cm, Um, and, unexpectedly , Am. Defined in vitro analyses revealed that tRNA Met(CAU) and tRNA Trp(CCA) are substrates for Cm formation, tRNA Gln(UUG) , tRNA Pro(UGG) , tRNA Pro(CGG) and tRNA His(GUG) for Um, and tRNA Pro(GGG) for Am. tRNA Ser(UGA) , previously observed as a TrmJ sub-strate in Escherichia coli, was not modified by PA14 TrmJ. Position 32 was confirmed as the TrmJ target for Am in tRNA Pro(GGG) and Um in tRNA Gln(UUG) by mass spectrometric analysis. Crystal structures of the free catalytic N-terminal domain of TrmJ show a 2-fold symmetrical dimer with an active site located at the interface between the monomers and a flexible basic loop positioned to bind tRNA, with confor-mational changes upon binding of the SAM-analog sinefungin. The loss of TrmJ rendered PA14 sensitive to H 2 O 2 exposure, with reduced expression of oxyR-recG, katB-ankB, and katE. These results reveal that TrmJ is a tRNA:Cm32/Um32/Am32 methyl-transferase involved in translational fidelity and the oxidative stress response.
Domains
Life Sciences [q-bio]
Origin : Publication funded by an institution
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