Albany 2013: Book of Abstracts

category image Albany 2013
Conversation 18
June 11-15 2013
©Adenine Press (2012)

High-resolution cryo-EM structure of the Trypanosoma brucei 80S: A unique eukaryotic ribosome

Eukaryotic 80S ribosomes of known structure are far more complex than their 70S bacterial counterparts. Those from Saccharomyces cerevisiae, Tetrahymena thermophila, and Triticum aestivum, for example, bear insertions of ribosomal RNA (rRNA) called expansion segments (ES) and additional ribosomal proteins. The ribosomes of the kinetoplastid Trypanosoma brucei, though, are especially fascinating: structurally, their and other kinetoplastids’ ribosomes bear very large ESs as well as smaller ESs and protein extensions. Additionally, T. brucei ribosomes require novel protein factors for maturation, although they do not require several eukaryotic initiation factors or a recycling factor. As a species, T. brucei is fascinating not only in terms of structure, but also in terms of gene expression and even public health: the species is responsible for the incurable, terminal Human African Trypanosomiasis (sleeping sickness); and during posttranscriptional regulation, a single common RNA segment called a splice leader is trans-spliced onto the 5’ ends of many of T. brucei’s mRNAs. The purpose of this splice event in translation is unknown.

Here, we present a high-resolution structure of the T. brucei ribosome, which contributes a great deal to addressing the above unknowns. We have employed map segmentation, homology modeling, ab initio rRNA modeling, and Molecular Dynamics Flexible Fitting (MDFF) to model the ribosome’s atomic structure. The positions and structures of the ribosome’s novel ESs and protein extensions were previously unknown, but our structure reveals the precise spatial contexts of these components. With this information in hand, we can begin to decipher T. brucei’s unusual translation requirements.

Amy Jobe 6
Yaser Hashem1
Amedee des Georges2
Jie Fu2
Sarah N. Buss3
Fabrice Jossinet4
Qin Zhang5
Hstau Y. Liao2
Bob Grassucci1
Chandrajit Bajaj5
Susan Madison-Antenucci3
Eric Westhof4
Joachim Frank1,2,6

1 HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
2 Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
3 Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, USA.
4 Architecture et Réactivité de l’ARN, Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire (CNRS), Strasbourg, France.
5 Department of Computer Science, Institute for Computational Engineering and Sciences, University of Texas, Austin, TX, USA.
6 Department of Biological Sciences, Columbia University, New York, NY, USA.