Mollusk shell acidic proteins: in search of individual functions.

Acidic proteins play a major role in the biomineralization process. These proteins are generally thought to control mineral formation and growth. Thus, characterization of individual acidic proteins is important as a first step toward linking function to individual proteins, which is our ultimate goal. In order to characterize the protein(s) responsible for the assemblage of biominerals, a new gel electrophoresis fixing and staining protocol was developed and many, if not all of the acidic proteins were visualized on the gel for the first time. In an in vitro assay we show that proteins extracted from an aragonitic shell layer induce the formation of amorphous calcium carbonate prior to its transformation into the aragonitic crystalline form. This study removes some major obstacles in the characterization of acidic proteins and sheds more light on the functions of these proteins in the biomineralization process.