Transcript Ribosomes - Understanding Evolution

Evolution connection: Ribosomes
Learning goals:
Students will understand that 1) some antibiotics work by attacking the
ribosome, 2) tiny differences that evolved in the ribosomes of prokaryotes
and eukaryotes are responsible for the specificity of those drugs towards
bacterial ribosomes, 3) our mitochondria are vulnerable to such drugs
because these organelles evolved via endosymbiosis from bacteria, and 4)
our evolutionary history matters in our everyday lives.
For the instructor:
This short slide set connects the topic of cellular ribosomes to both our
evolutionary history and modern medicine. Slide 9 may be skipped to save
time. Throughout the notes, optional information is included in parentheses
in case the instructor wants to go into more detail. To integrate these slides
best, use them immediately after you’ve discussed the structure of
ribosomes and their role in the cell. Alternatively, you may wish to use these
slides when you discuss translation later in the semester.
Evolution connection: Ribosomes
Ribosomes: An achilles heel for bacteria
Petri dish photo from CDC; researcher photo from CDC/Dr. U.P. Kokko; photo of various
medicines from National Institute of Health
Evolution connection: Ribosomes
Why don’t antibiotics like streptomycin
harm our own cells?
Evolution connection: Ribosomes
Ribosomes evolved early in the history of life
All ribosomes
share:
• similar rRNA
sequences
• small subunit that
decodes mRNA
• large subunit that
joins amino acids
together
The ribosome
evolved back
here.
Evolution connection: Ribosomes
Ribosomes evolved early in the history of life
Small
evolutionary
changes  big
impact
The ribosome
evolved back
here.
... and evolved
modifications
as life’s lineages
diversified.
Evolution connection: Ribosomes
Streptomycin-like antibiotics bind to the ribosome
Antibiotic binds here and interferes with protein
synthesis …
A site
antibiotic
ribosome
… but not in eukaryotic ribosomes.
Evolution connection: Ribosomes
Streptomycin-like antibiotics can’t bind to the
eukaryotic ribosome …
… because of
position 1408
In the small
ribosomal
subunit.
G
A
Evolution connection: Ribosomes
Streptomycin-like antibiotics can’t bind to the eukaryotic
ribosome …
Images provided by Joseph D. Puglisi.
Evolution connection: Ribosomes
But eukaryotic mitochondrial ribosomes are
vulnerable.
Mitochondrion
G
ribosomes
A
References
Bokov, K., and Steinberg, S. V. (2009). A hierarchical model for evolution of
23S ribosomal RNA. Nature. 457: 977-980.
Lynch, S. R., and Puglisi, J. D. (2001). Structural origins of aminoglycoside
specificity for prokaryotic ribosomes. Journal of Molecular Biology. 306: 10371058.
Pace, N. R. (1997). A molecular view of microbial diversity and the biosphere.
Science. 276: 734-740.
Recht, M. I., Douthwaite, S., and Puglisi, J. D. (1999). Basis for prokaryotic
specificity of action of aminoglycoside antibiotics. The EMBO Journal. 18:
3133-3138.
Selimoglu, E. (2007). Aminoglycoside-induced ototoxicity. Current
Pharmaceutical Design. 13: 119-126.