Master of Science (MS)
Chemistry and Biochemistry
First Committee Member
Second Committee Member
Third Committee Member
Fourth Committee Member
Number of Pages
Protein quality control (PQC) is a critical process wherein misfolded or damaged proteins are cleared from the cell to maintain protein homeostasis. In eukaryotic cells, the removal of misfolded proteins is primarily accomplished by the ubiquitin-proteasome system (UPS). In the UPS, ubiquitin-conjugating enzymes and ubiquitin ligases append poly-ubiquitin chains onto misfolded protein substrates signaling for their degradation. The kinetics of protein ubiquitylation are paramount since a balance must be achieved between the rapid removal of misfolded proteins versus providing sufficient time for protein chaperones to attempt refolding. To uncover the molecular basis for how PQC substrate ubiquitylation rates are controlled, the reaction catalyzed by nuclear ubiquitin ligase San1 was reconstituted in vitro. Our results demonstrate that San1 can function with 2 ubiquitin-conjugating enzymes, Cdc34 and Ubc1. While Cdc34 and Ubc1 are both sufficient for promoting San1 activity, San1 functions preferentially with Ubc1, including when both Ubc1 and Cdc34 are present. Notably, a homogeneous peptide that mimics a misfolded PQC substrate was developed and enabled quantification of the kinetics of San1-catalyzed ubiquitylation reactions. We discuss how these results may have broad implications for the regulation of PQC-mediated protein degradation.
Protein Degradation; Protein Misfolding; Protein Quality Control; Ubiquitin; Ubiquitin-Conjugating Enzyme; Ubiquitin Ligase
Biochemistry | Chemistry
University of Nevada, Las Vegas
Ibarra, Rebeca Lea, "The San1 Ubiquitin Ligase Functions Preferentially with Ubiquitin-Conjugating Enzyme Ubc1 During Protein Quality Control" (2016). UNLV Theses, Dissertations, Professional Papers, and Capstones. 2783.
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