Year of Award

2008

Document Type

Thesis

Degree Type

Master of Science (MS)

Other Degree Name/Area of Focus

Biochemistry Program

Department or School/College

Division of Biological Sciences

Committee Chair

Michele A. McGuirl

Commitee Members

Bruce Bowler, Scott Wetzel

Keywords

beta oligomer, fibril, Isoforms, misfolded prion, Prion, solvent accessibility, tryptophan fluorescence quenching

Abstract

Conversion of prion protein (PrP) from its normal, cellular isoform, PrPC, to an infectious, misfolded, fibrillar isoform, PrPSc, is responsible for various neurodegenerative diseases in a variety of mammalian hosts. Although the structure of PrPC is well studied, the structure of PrPSc is not known. Obtaining structural information on the misfolded isoform of prion may lead to preventative therapies and treatments of prion diseases. In this study, six single-tryptophan mutants of recombinant PrP were expressed, purified, and refolded into PrPC or two misfolded isoforms of prion, PrPb and PrPF. Solvent accessibilities of the six tryptophan residues were probed among the three isoforms using various tryptophan fluorescence techniques. For all six mutants, solvent accessibility was shown to decrease following conversion to the misfolded isoforms. Tryptophan accessibility data was used to evaluate two computational models of PrPSc, the beta-helix model and the-beta spiral model, and was also compared with experimental data in literature. Although neither computational model entirely fit the data, the Surewicz model of parallel, in-register beta-strands comprising residues ~160-220 was in agreement with tryptophan accessibilities of residues within this area. However, more structural detail of this experimentally-based model is needed before the two data sets can be fully compared.

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© Copyright 2008 Jessica Louise Gilbert