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