Temporal Distribution of L-Dopa-Containing Proteins Involved in Oyster Shell Formation

Marine bivalve organisms such as Crassostrea virginica (eastern oyster) produce structural proteins that are critical in adhesive strategies and shell biomineralization. The unique properties of these proteins derive from the amino acid composition. L-3,4-dihydroxyphenylalanine (L-dopa), which is a unique key amino acid in the cross-linking of these proteins, can be considered a biomarker for identification and localization of shell formation proteins. The focus of this research was to determine the distribution of L-dopa-containing proteins involved in the process of biomineralization in the eastern oyster, Crassostrea virginica. Three organismal compartments were identified as sources of L-dopa protein pre-cursors: hemocytes, cell-free hemolymph, and mantle tissue. Hemolymph was harvested from the adductor muscle of notched oysters and hemocytes were subsequently collected via hemolymph centrifugation. Mantle tissue was collected from either side of the notch area, as well as the anterior portion. The product of repair, nascent shell deposited in the notch, was collected from the notch site at discrete time points post-notching. Amino acid composition was determined via anion exchange HPLC with pulsed amperometric detection. L-dopa concentration was related to the time since notching: we have preliminary information that indicated a higher level of L-dopa concentration in hemocytes 24-28 hours post notching and in hemolymph at 96 hours post notching, indicating an induction of resources for notch repair. L-dopa was found in higher levels in nascent repair shell and declined as the shell aged indicating protein cross-linking. These data support the premise that L-dopa-containing proteins are involved in oyster shell formation and that they are distributed among several components and products within the system