Structural characterization of ribosome recycling and fusidic acid inhibition in Staphylococcus aureus

During bacterial ribosome recycling, 70S ribosomes are split into subunits by ribosome recycling factor (RRF) and elongation factor G (EF-G). The antibiotic fusidic acid (FA) inhibits elongation and ribosome recycling by locking EF-G to the ribosome. Yet, no functional ribosome recycling FA complex has been successfully captured. Here we used single-particle cryo-electron microscopy to resolve multiple FA-stalled intermediates of Staphylococcus aureus ribosomes, including a previously unobserved complex containing both RRF and EF-G. Our structures reveal how RRF and EF-G jointly disrupt inter-subunit bridges, promote back-rotation of the small subunit, and destabilize the tRNA to facilitate ribosome splitting. We further show that FA predominantly inhibits recycling by trapping EF-G on the post-termination complex in the absence of RRF, preventing formation of the active RRF*EF-G complex. These insights advance understanding of the molecular mechanism of bacterial ribosome recycling and the mode of action of FA as an antibiotic. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/721003v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@12951c2org.highwire.dtl.DTLVardef@1b6b7f3org.highwire.dtl.DTLVardef@e6cc04org.highwire.dtl.DTLVardef@5c4521_HPS_FORMAT_FIGEXP M_FIG C_FIG