engleski

Novel insights into structural basis of antibiotic resistance in type II isoleucyl-tRNA synthetases

Isoleucyl-tRNA synthetases (IleRS), evolutionarily conserved enzymes, covalently couple isoleucine, via isoleucyl-adenylate intermediate to its cognate tRNAIle in the process of protein biosynthesis. Bacterial IleRS, which are phylogenetically clustered into two different clades (IleRS1 and IleRS2) show different levels of susceptibility for competitive inhibition with mupirocin, a naturally produced antibiotic from the bacterium Pseudomonas fluorescens. IleRS1, present in most pathogenic bacteria, are up to 9 orders of magnitude more susceptible for mupirocin inhibition than bacterial IleRS2 which share structural similarities with eucaryotic IleRS, thus making IleRS1 favorable pharmaceutical targets. Although differences in mupirocin inhibition between two types of IleRS are known, the exact reason for the difference remained unsolved, partly because of a limited number of crystall structures of mupirocin-bound IleRS. To investigate reasons of different mupirocin affinity of the two IleRS types, crystall structures of Bacillus megaterium IleRS1 and ileRS2 in complex with mupirocin and the nonhydrolyzable analog of the reaction intermediate, Ile-AMS, were solved. By mutually comparing the structures, we have shown that mupirocin binding in IleRS1 and IleRS2, although highly similar, is not completely analogous. The active site of IleRS1 is compact and preformed for high-affinity mupirocin binding, while binding of mupirocin to the IleRS2 active site coincides with surprisingly drastic steric rearrangement of key active site parts. By avoiding to attribute differences in IleRS1 and IleRS2 mupirocin affinity only to the interaction pattern of mupirocin in the active sites of the enzymes, we share a new light on how differences in mupirocin resistance od IleRS1 and IleRS2 are directly correlated to steric rearrangements (or lack thereof) of the active site upon mupirocin binding.

isoleucyl-tRNA-synthetase ; mupirocin ; structure ; IleRS1 ; IleRS2

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