How hibernation factors RMF, HPF, and YfiA turn off protein synthesis.

Eubacteria inactivate their ribosomes as 100S dimers or 70S monomers upon entry into stationary phase. In Escherichia coli, 100S dimer formation is mediated by ribosome modulation factor (RMF) and hibernation promoting factor (HPF), or alternatively, the YfiA protein inactivates ribosomes as 70S monomers. Here, we present high-resolution crystal structures of the Thermus thermophilus 70S ribosome in complex with each of these stationary-phase factors. The binding site of RMF overlaps with that of the messenger RNA (mRNA) Shine-Dalgarno sequence, which prevents the interaction between the mRNA and the 16S ribosomal RNA. The nearly identical binding sites of HPF and YfiA overlap with those of the mRNA, transfer RNA, and initiation factors, which prevents translation initiation. The binding of RMF and HPF, but not YfiA, to the ribosome induces a conformational change of the 30S head domain that promotes 100S dimer formation.

Figure: Unbiased (Fobs - Fcalc) difference Fourier maps of hibernation factors in complex with the T. thermophilus 70S ribosomes. The unbiased difference electron densities are contoured at 2.2, 2.5, and 2.7 σ for RMF (A), HPF (B) and YfiA (C), respectively. The refined models of RMF (blue), HPF (green), and YfiA (yellow) are displayed in their respective electron densities for clarity. The inset in (A) is a close-up view of the RMF electron density in the region between Trp40 and Trp44.

Results from:
Armstrong AA, Mohideen F, Lima CD.
Nature. 2012 Feb 29;483(7387):59-63. doi: 10.1038/nature10883.
PMID: 22382979 [PubMed - indexed for MEDLINE]
PMCID: PMC3306252