Antibiotic resistance in bacteria is becoming a major threat to public health. Many of
the antibiotics used today in the clinic target the process of protein synthesis
performed by the ribosome. Recent prospects for blocking ribosome function are
increasingly focusing on preventing the assembly of bacterial ribosomes. A number of
ribosome assembly factors are emerging as attractive targets for novel antibiotics that
work in new ways.
YphC and YsxC are essential GTPases in Bacillus subtilis that facilitate the assembly
of the 50S ribosomal subunit; however, their roles in this process are still
uncharacterized. To explore their function, we biochemically and structurally
characterized the 45SYphC and 44.5SYsxC precursor particles accumulated from strains
depleted of YphC and YsxC, respectively. Quantitative mass spectrometry analysis
and 5-6 Å resolution cryo-EM maps of the 45SYphC and 44.5SYsxC particles revealed
that the two GTPases participate in maturation of functional sites of the 50S subunit.
We also observed that YphC and YsxC bind specifically to the two immature particles.
In addition, we characterized the structure of the 50S subunits in complex with the
RbgA protein. The preliminary 3D structure shows that the RbgA protein binds to the
P site of the 50S subunit and displaces h69. There are also missing densities in the
structure for h68 and the uL16 ribosomal protein. We expect that the atomic
resolution structure of the 50S.RbgA complex will reveal the function and molecular
mechanisms of this assembly factor.
The deep structural understanding of protein synthesis process done by the ribosome
led to the optimization of over a hundred antibiotics that are currently used in thev
clinic. In the same manner, work described in this thesis provides novel insights into
understanding the maturation of the large ribosomal subunit, and is paving the way to
use the bacterial ribosome biogenesis pathway as a target for the development of new
antimicrobials. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/20974 |
| Date | January 2017 |
| Creators | Ni, Xiaodan |
| Contributors | Ortega, Joaquin, Biochemistry and Biomedical Sciences |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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