Date of Award


Document Type


Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

Geoff Lin-Cereghino

First Committee Member

Eric Thomas

Second Committee Member

Craig Vierra

Third Committee Member

Andreas Franz


Pichia pastoris, a methylotrophic yeast, is an ideal host for recombinant protein expression. It has the capability of performing many eukaryotic post-translational modifications and grows to high cell densities. However, P. pastoris’s secretion properties are not always efficient, and its secretory pathway mechanisms have not been thoroughly elucidated. A previously identified mutant strain, bgs13, was found to efficiently secrete most recombinant proteins tested, raising the possibility that this bgs13 mutant is a universal super secreter and understanding its secretion process is needed. In this study, we used a reporter protein, ?-lactoglobulin (b-LG), to perform structural analysis and comparisons of protein secreted from wild type and mutant bgs13 strains of Pichia pastoris. Primary, secondary, and tertiary structure of b-LG were examined using Edman sequencing, circular dichroism, and tryptophan fluorescence. Our results suggest that the mutant strain improves the folding of b-LG, affecting its tertiary structure. Understanding the enhanced folding ability of bgs13 will provide insight into the secretory mechanism of P. pastoris, which will allow for further improvement and use of P. pastoris as an optimal host for protein production.





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