The RNA helicase HrpA rescues collided ribosomes in E. coli

Abstract

Although many antibiotics inhibit bacterial ribosomes, loss of known factors that rescue stalled ribosomes does not lead to robust antibiotic sensitivity in E. coli, suggesting the existence of additional mechanisms. Here, we show that the RNA helicase HrpA rescues stalled ribosomes in E. coli. Acting selectively on ribosomes that have collided, HrpA uses ATP hydrolysis to split stalled ribosomes into subunits. Cryo-EM structures reveal how HrpA simultaneously binds to two collided ribosomes, explaining its selectivity, and how its helicase module engages downstream mRNA, such that by exerting a pulling force on the mRNA, it would destabilize the stalled ribosome. These studies show that ribosome splitting is a conserved mechanism that allows proteobacteria to tolerate ribosome-targeting antibiotics.