Date of Award

5-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Biological Sciences

Advisor

Wheeler, Hap P

Committee Member

Colacino , Jim

Committee Member

Burnett , Karen

Committee Member

Montanucci , Richard

Abstract

The soluble organic matrix (SM) extracted from the shell of the Eastern oyster, Crassostrea virginica was analyzed to identify the constituent proteins and their structures. Two acidic proteins with estimated molecular weights of 48 and 55 kD were isolated and determined to have highly related structures. Both proteins are comprised primarily of aspartate, serine, and glycine which represent nearly 90% of the total amino acids. Studies indicate that both proteins are phosphorylated and have estimated isoelectric points in the range of 3 to 5. Evidence suggests that poly-aspartate and poly-serine domains are present in the 48 kD protein. Amino terminal sequences were determined to be D-E-A-D-A-G-D-A-Y-D-V-A-D-T, for the 48 kD protein, and S-K-G-X-E-P-D, for the 55 kD protein where, X may be phosphoserine. Immuno-analyses using antibodies generated to the 48 and 55 kD proteins revealed that they share many common epitopes. Additional proteins were identified in SM by these antibodies indicating that the 48 and 55 kD proteins are members of a prominent acidic protein family. The acidic character of the 48 and 55 kD proteins, and their presence in the shell and extra-pallial fluid supports the hypothesis that they function in shell formation.
The SM from 14 bivalve species was compared in order to determine whether or not specific matrix protein components correlate with shell microstructure or mineralogy. While the compositions from all species were enriched in acidic amino acids, SM derived from calcite shell, including prismatic and foliated microstructures, was determined to be more acidic than aragonite. A prominent phosphoprotein class was identified in folia SM by electrophoresis and appears unique to species having this microstructure. Electrophoretic protein patterns of aragonite SM were more variable and may reflect its earlier appearance in the geologic record compared to calcitic shell structures. ELISA experiments using an antibody generated to the SM of the Eastern oyster demonstrated highest cross-reactivity among related species, irrespective of shell structure. Western analysis shows broad reactivity to component proteins among all species. Apart from the folia microstructure, there was no particular protein pattern that correlated with a specific shell structure, rather SM protein patterns were determined to be species specific.

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Zoology Commons

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