Abstract
The TRAFAC (translation factors) GTPase OLA1 plays a critical role in various stress responses and is implicated in the regulation of tumor progression. It is conserved from bacteria to eukaryotes and regulates the translation through binding to the ribosome. Here, we report the cryo-electron microscopy structure of its Escherichia coli homolog, YchF, with the 50S subunit. In this structure, YchF is positioned at the side of the 50S subunit by engaging with uL14, bL19, and rRNA helix H62 through its helical and ATPase domains. We further demonstrate that the helical domain is essential for OLA1/YchF to function. A comprehensive analysis of the structure and Ribo-seq data points out that OLA1/YchF promotes the splitting of ribosomes into subunits on D/E-rich mRNA. Our findings provide crucial structural insights into the molecular mechanism of OLA1/YchF-associated translation-stalling regulation, which maintains the translation of genes involved in stress response and tumor progression.