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Date of Award

2013

Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)

Department

Biological Sciences

First Advisor

Craig A. Vierra

First Committee Member

Geoff Lin-Cereghino

Second Committee Member

Lisa Wrischnik

Abstract

Spider silk is a natural high-performance biopolymer with superior mechanical propetiies. Although these fibers out perfmm several man-made and natural biomaterials, there are cha llenges to be circumvented before commercialization. One of the silkproducing glands warranting further study is the pyrifonn gland, which produces gluelike threads functioning to cement dragline silk to substrates. We focused on the molecular properties of PySp 1, the major component of pyrifonn silk from Latrodectus hersperus, and its putative Oiiholog, PySp2, from Nephi/a clavipes. To date, there are no reports describing the secondary structure of PySp internal block repeats. Moreover, because the PySp C-terminus amino acid residues are distinct from MaSp C-terminus and the morphology of these glands is different, we hypothesized that PySp C-terminal domains form distinct secondary structures. The MaSp C-terminus has been shown to regulate the silk assembly process and whether the PySp C-terminus performs a similar function is unknown. In order to test this supposition, we used the following experimental approaches: I) we developed a series of PySp prokaryotic expression constructs carrying various block repeat modules representative of the internal iterations found within the protein chain; 2) we constructed prokaryotic expression vectors coding for the PySp C-terminal domains; 3) we expressed and purified the PySp C-terminal domains from bacteria; 4) we performed structural analyses of the purified PySp C-terminal domains using cd spectroscopy and atomic force microscopy. After expression and purification of the PySp C-tennini proteins, our studies support that this domain displays a predominantly ~-sheet structure, distinctive from the NMR-determined ahelical nature of MaSp C-tennini. The difference in secondary structure implies the MA and pyriform glands use different biochemical mechanisms during fiber extrusion to control protein folding and assembly. By investigating protein folding and fiber formation for different spider silk types, its characteristics can be customized for spinning different materials for industrial applications.

Pages

120

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