Mycobacterial HflX is a ribosome splitting factor that mediates antibiotic resistance

Abstract

Antibiotic resistance in bacteria is typically conferred by proteins that function as efflux pumps or enzymes that modify either the drug or the antibiotic target. Here we report an unusual mechanism of resistance to macrolide-lincosamide antibiotics mediated by mycobacterial HflX, a conserved ribosome-associated GTPase. We show that deletion of thehflXgene in the pathogenicMycobacterium abscessus, as well as the nonpathogenicMycobacterium smegmatis, results in hypersensitivity to the macrolide-lincosamide class of antibiotics. Importantly, the level of resistance provided byMab_hflXis equivalent to that conferred byerm41, implying thathflXconstitutes a significant resistance determinant inM. abscessus. We demonstrate that mycobacterial HflX associates with the 50S ribosomal subunits in vivo and can dissociate purified 70S ribosomes in vitro, independent of GTP hydrolysis. The absence of HflX in aΔMs_hflXstrain also results in a significant accumulation of 70S ribosomes upon erythromycin exposure. Finally, a deletion of either the N-terminal or the C-terminal domain of HflX abrogates ribosome splitting and concomitantly abolishes the ability of mutant proteins to mediate antibiotic tolerance. Together, our results suggest a mechanism of macrolide-lincosamide resistance in which the mycobacterial HflX dissociates antibiotic-stalled ribosomes and rescues the bound mRNA. Given the widespread presence ofhflXgenes, we anticipate this as a generalized mechanism of macrolide resistance used by several bacteria.