The homology of biomineralization pathways is underlined by a remarkable experiment whereby the nacreous layer of a molluscan shell was implanted into a human tooth, and rather than experiencing an immune response, the molluscan nacre was incorporated into the host bone matrix.
12.
In oysters and potentially most molluscs, the nacreous layer has an organic framework of the protein MSI60, which has a structure a little like spider silk and forms sheets; Aspartic acid, which can make up up to 50 % of shell framework proteins, is most abundant in calcitic layers, and also heavily present in aragonitic layers.
