evolution connection: ribosomes

Evolution connection: RibosomesEvolution 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.


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

Why don’t antibiotics like streptomycin harm our own cells?



Ribosomes evolved early in the history of life

All ribosomesshare:

• similar rRNA sequences

• small subunit that decodes mRNA

• large subunit that joins amino acids together

The ribosomeevolved back

here.


Ribosomes evolved early in the history of life

The ribosomeevolved back

here.

... and evolvedmodificationsas life’s lineagesdiversified.

Small evolutionary changes big impact


Streptomycin-like antibiotics bind to the ribosome

Antibiotic binds here and interferes with protein synthesis …

… but not in eukaryotic ribosomes.

A site antibiotic

ribosome


… because ofposition 1408In the small ribosomalsubunit.

Streptomycin-like antibiotics can’t bind to theeukaryotic ribosome …

G A


Streptomycin-like antibiotics can’t bind to the eukaryoticribosome …

Images provided by Joseph D. Puglisi.


But eukaryotic mitochondrial ribosomes are vulnerable.

G A

Mitochondrion

ribosomes

ReferencesReferences

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: 1037-1058.

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.

evolution connection: ribosomes

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