Compartmentalization and Temporal Distribution of L-Dopa-Containing Proteins Involved in Oyster Shell Formation
Marine molluscs, such as Crassostrea virginica (eastern oyster), produce structural proteins that are essential 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 compartmentalization of Ldopa-containing proteins involved in the process of biomineralization in C. virginica at different time points during a shell repair event. Three organismal compartments were identified as possible locations of L-dopa precursor proteins: 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 specific locations. The product of repair, nascent shell deposited in the notch, was collected at discrete time points post-notching. Amino acid composition related to time since notching was determined via anion exchange HPLC with pulsed amperometric detection. Additionally, the Arnow Assay (specific for catechols) was used to stain for L-dopa in the samples. Preliminary data reveal increased L-dopa concentrations in hemocytes and hemolymph at 24-48 hours and 96 hours post notching, respectively, indicating a mobilization of resources for shell repair. These data support the hypothesis that L-dopa-containing proteins are involved in oyster shell formation and that they are distributed at discrete locations within the organism.