Project Summary/Abstract
In biology, there are two fundamental conflicts: the conflicts between organisms and the conflicts
between organisms and viruses. During the conflicts, a variety of offensive and defensive weaponry are
employed by organisms and viruses. While the molecular mechanisms of the conflicts between organisms
and viruses have been extensively studied, significantly less have been carried out with the conflicts
between organisms. During the conflicts between organisms, protein toxins are frequently employed as the
offensive weapons. Among them, ribotoxins constitutes one of the biggest groups. In fact, colicin E3 was
the first ribotoxin to be characterized 50 years ago. It makes a single but precise cut of 16S rRNA in the
decoding center of bacterial ribosome, resulting in stalled ribosome and eventual cell death. Over the last
half of a century, it is unclear whether there exists a biological system that is able to reverse the ribosomal
damage by colicin E3 to allow cell to survive. Employing approaches of bioinformatics, biochemistry,
structural biology, and microbiology, we have uncovered a bacterial two-component system, RtcB and PrfH,
as the antidote of colicin E3. Specifically, bacterial PrfH recognizes the damaged and stalled ribosome and
performs ribosomal rescue. This is followed by RtcB repairing the damaged 30S ribosomal subunit. The
sequential events described above are supported by abundant preliminary data from both our in vitro and in
vivo studies. In this application, we plan to significantly expand our preliminary studies to systematically
characterize the rescue and repair of bacterial ribosome with specific damage in the decoding center with
the following three main aims: 1) We will provide insight into bacterial PrfH recognizing and rescuing the
damaged and stalled 70S ribosome in vitro; 2) We will biochemically and structurally characterize bacterial
RtcB in vitro, with the emphasis of PrfH-coupled RtcB repairing the damaged 30S ribosomal subunit; and 3)
We will elucidate in vivo biological functions of RtcB-PrfH using an in vivo attenuated RNA damage system
we have developed.