We have a collaborative project on proteins that are involved in biomineralization. Some of the accomplishments in this area are given below.

• We have purified two major proteins which contribute significantly to calcium carbonate crystallization and biomineralization in chicken (OC-17) and goose egg shells (ansocalcin). We have completed the amino acid sequences of these proteins. Both proteins are structurally similar to C-type lectin like proteins. Ansocalcin induced the formation of polycrystalline calcite crystal aggregates whereas OC-17 has little influence morphology of calcite crystals. We have designed short peptides based on its structure which mimic parent protein.

 

• Unlike other avian eggshells, quail eggshells do not contain any C-type lectin like proteins. We have shown that quail eggshells contain ovomucoid as the major component and had no influence on the eggshell morphology. However, the whole eggshell extract altered the morphology of calcite crystals through an amorphous calcium carbonate (ACC) precursor phase.

 

• We also purified pelovaterin from turtle eggshells. This protein induces the formation of vaterite crystals. It is a 42-residue protein. Its solution structure shows that it folds similar to β-defensins. This protein also shows some antibacterial activity.

• Under abiotic conditions, it is difficult to replace >7% Ca2+ by Mg2+ ions into calcite crystal lattice. We have shown that the endoskeleton of starfish from Santa Barbara contains up to ~20% of Mg2+ ions in the calcite lattice which confers excellent mechanical strength. We have also shown that the tight regulation of crystal morphology is controlled by magnesium ions and the soluble matrix proteins through amorphous precursors.

Key Publications