Year: 2017
Type: dissertation
Abstract: Oligomerization and ubiquitylation are fundamental to the function of many proteins. Protein oligomerization confers numerous advantages including allosteric regulation, increased coding efficiency, and reduced transcriptional and translational error rates. Ubiquitylation is a widespread post-translational modification that targets modified proteins to a variety of fates including degradation by the 26S proteasome. Dysfunctional protein degradation is a common mechanism shared by a diverse range of human diseases. Many members of the BTB domain superfamily have roles centered on protein oligomerization and ubiquitylation. The BTB domain can facilitate self-assembly to form dimers, tetramers, and pentamers. In addition, many BTB proteins provide substrate specificity for the Cullin3 (Cul3) E3 ubiquitin ligase. Dysfunctional BTB/Cullin3 ubiquitinylation complexes are involved in certain forms of prostate cancer, medulloblastoma, hereditary hypertension and other diseases. Thus, understanding the details of BTB protein oligomerization and Cul3 interaction is important towards many aspects of human disease. The research presented in this thesis addresses several areas of BTB/Cul3 biology. The mechanism of dimeric BTB protein to Cul3 association was expanded to include the contributions from the BACK domain observed in the crystal structure of KLHL3/Cul3. Several KLHL3 mutations associated with familial hypertension were found to disrupt Cul3 binding. Next, the structure and oligomeric state of several KCTD family BTB proteins were investigated and found to be pentameric instead of tetrameric. The Cul3 binding properties of several KCTD proteins were characterized and found to be heterogeneous in contrast to other BTB protein families. The structural and functional properties of several KCTD proteins were used to propose a mechanism of KCTD/Cul3 association and the determinants for Cul3 binding. Finally, the structure of the KCTD5/Cul3/Gβγ complex was characterized and the binding affinities of Cul3 and Gβγ to KCTD5 were determined. Overall, these results provide insight into the assembly of multimeric BTB/Cul3 ubiquitylation complexes.
Source: TSpace (University of Toronto)
Author: Xian Ji
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
Funder: University of Toronto
OpenAlex ID: W2944470746