On self-organized shell formation by bovine carbonic anhydrase II, and soluble protein extracted from regenerated shell.

The soluble protein of hemocytes from diseased shell (HDS) of oyster, Crassostrea gigas, was shown to play a key role in the rapid growth of calcium carbonate crystals. In this study, we compared HDS extracted from regenerated (or diseased) shell with bovine carbonic anhydrase II in terms of their ability to promote the growth of calcium carbonate crystals. On the basis of scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) analysis, a high growth rate of calcium carbonate crystals was identified under artificial seawater and atmospheric temperature. The function and role of HDS extracted from regenerated shell are discussed at the molecular point as compared to aragonite-specific soluble proteins. Our findings suggest that hemocytes function as a soluble protein, with repeated GX (G: Gly, X: Asp, Asn or Glu) or negative charged amino acid domains binding calcium and specific surface features for catalyzing rapid shell regeneration.

Nano-structured biogenic calcite: a thermal and chemical approach to folia in oyster shell.

The thin sheets of calcite in oyster shell in Crassostrea gigas are termed folia and comprise much of the oyster shell. The folia are covered by a layer of discrete globules that has been proposed to consist of aggregations of an organic matrix and minerals. A continuous organic framework divides each tablet into nanograins. Their shape is globular with a mean extension from 30 to 40 nm. Chemical and thermal treatments to correlate between the organic matrix and the minerals are considered using spectrometers, thermal analyzers, and electron microscopes. After treatment, the nanograins of the foliar and organic matrix are clearly identified. The organic matrix plays a key role in the thermal stability and material properties of this biological composite. From analysis of the FT-IR results, it is identified that the organic matrix in folia is composed of proteins and polysaccharides.

The correlation between organic matrices and biominerals (myostracal prism and folia) of the adult oyster shell, Crassostrea gigas.

The organic membrane at the interface between the myostracum (aragonite) and folia (calcite) was obtained and identified as a chitin-like macromolecule after chemical treatment. It was confirmed that the organic membrane was faced to the crystal (001) plane of the myostracum and folia. The secondary structures in soluble protein of the myostracum and the folia of oyster shell were identified as a great quantity of beta-structure. The acidic amino acids, Asp and Glu, to play a role as templates on shell formation were confirmed in the myostracum and the folia.

Primary structure of myostracal prism soluble protein (MPSP) in oyster shell, Crassostrea gigas.

Soluble protein (MPSP, myostracal prism soluble protein) obtained from myostracum in oyster shell (Crassostrea gigas) was characterized using biochemical and molecular biological techniques. From an analysis of secondary protein structure, it was shown that beta-structure was predominant in MPSP. And via in vitro assays, the relation of MPSP to biomineral phase and morphology was studied. SDS-PAGE revealed one major protein band of 20 kDa. An amino acid sequence of 160 amino acids was deduced for myostracum by characterization of the complementary DNA encoding the protein. The deduced protein was composed of a high proportion of Gly and Asp, typifying a calcium-binding protein for shell formation, and a relatively high proportion of Val, Ala and Ile, typifying an adhesive protein. In contrast to prevailing expectations, (Gly-Asp)n-type sequence motifs exist in MPSP, demanding a revision of previous theories of protein-mineral interactions. The cDNA sequence of myostracum is elucidated for the first time.