Misfolding of membrane proteins as a result of mutations that disrupt their functions in substrate transport across the membrane or signal transduction is the cause of many significant human diseases. Yet, we still have a limited understanding of the direct consequences of these mutations on folding and function - a necessary step toward the rational design of corrective therapeutics. This thesis addresses the gap in understanding the residue-specific implications for folding through a series of experiments that utilize the cystic fibrosis transmembrane conductance regulator (CFTR) as a model in various contexts. We first examined the thermodynamic implications of mutations in the soluble nucleotide binding domain 1 (NBD1) of CFTR. We found that mutations can have a significant effect on thermodynamic stability that is masked in non-physiological conditions. Our studies were then focussed on a membrane-embedded hairpin CFTR fragment comprised of transmembrane segments 3 (TM3) and 4 (TM4) to evaluate the direct effects of mutations on folding in a systematic manner. It was found that the translocon-mediated membrane insertion of helices closely parallels a basic hydrophobic-aqueous partitioning event. This study was then extended to determine residue-specific effects on helix-helix association. We found that this process is not solely dependent on hydropathy, but there is a context dependence of these results with regard to residue position within the helix. Overall, these findings constitute a key step in relating mutation-derived effects on membrane protein folding to the underlying basis of human disease such as cystic fibrosis.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/34817 |
| Date | 18 December 2012 |
| Creators | Mulvihill, Cory Michael |
| Contributors | Deber, Charles M. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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