Investigation of the role of ansocalcin in the biomineralization in goose eggshell matrix

Abstract

The role of proteins in biomineralization and the mechanism of eggshell formation are not well understood. We have isolated and purified the major protein, ansocalcin from goose eggshell matrix. The amino acid sequence study indicates that ansocalcin is homologous to the chicken eggshell protein, ovocleidin 17, and C-type lectins. Ansocalcin nucleates polycrystalline aggregates of calcite crystals in in vitro mineralization experiments. The polycrystalline aggregates obtained at higher concentration of ansocalcin appears to be similar to the crystals observed at the mamillary layer of the eggshell.B iomineralization is commonly referred to as the formation of biocomposites consisting of layered assembly of biomacromolecules such as proteins with well ordered calcium-rich inorganic phase (1-3). This highly complex process involves a series of molecular events such as selective recognition and deposition of calcium salts by proteins followed by the formation of a mineral phase comprising crystallites of uniform size, crystallographic orientation, and morphology (4, 5). In most cases, the minerals are formed over a biomolecular scaffold or mold resulting in composite materials (6, 7). The role of such biologically programmed composites varies from skeletal tissues to protective shells against the predators (8, 9). These highly complex, hierarchically ordered and multifunctional composites are formed under mild conditions with size ranges from nano-to centimeter scale, exhibiting unusual mechanical properties that outperform synthetic materials (10-15). Such structures appeared to originate from organized assembly of biomacromolecules such as proteins, polysaccharides or proteoglycans, and the inorganic salt (16). The organic macromolecules act as templates through self-assembly to facilitate interaction with the insoluble matrix and to induce the desired stereochemistry for the construction of organized structures (17-19). Biomacromolecules are known to be involved in controlling the nucleation, growth, size, and shape of the mineral phases (20). Often these macromolecules are functionalized with acidic groups such as carboxylic acid, sulfonate, and phosphate moieties, which allow them to be an effective metal ion chelator to interact with the inorganic matrix (21-23).Avian eggshells present a unique and interesting model for exploring the process of biomineralization, in which CaCO 3 layers are created by the selective nucleation and deposition of calcite crystals by proteins. Moreover, the active sites on the protein recognize calcium ions and induce nucleation of specific polymorph of CaCO 3 and control the morphology of mineral phase. In the case of chicken eggshells, Ϸ5 g of CaCO 3 is deposited within 22 h in an acellular medium as the egg passes through the oviduct, which makes avian eggshells one of the fastest mineralized hard tissues in biological systems (24). The structure of an avian eggshell consists of two principal external layers, namely a membrane layer that surrounds the albumin and a calcified sh...

A Novel Protein Tightly Bound to Bacterial Magnetic Particles in Magnetospirillum magneticum Strain AMB-1

“…For the proteins that directly interact with biominerals, two plausible functions are suggested: (i) initiation of crystal nucleation (25,27,30) and (ii) inhibition and regulation of crystal growth (24,31) and determination of morphology (32,33). The initiation starts from the interaction and accumulation of metal ions on or in the organic molecules.…”

Formation of magnetite by bacteria and its application

“…Organic molecules tightly or directly associated with biominerals often play key roles in the initiation or the growth regulation of crystal sizes and morphologies (Belcher et al 1996;Shimizu et al 1998;Lakshminarayanan et al 2002). Detailed analyses of the biological processes have allowed us to use or mimic them for creating a new generation of synthetic materials (Sugawara et al 2003;Nuraje et al 2006;Sano et al 2006).…”

MMS6 Protein Regulates Crystal Morphology during Nano-sized Magnetite Biomineralization in Vivo

“…These biomineralization mechanisms have captured the imagination of material scientists engaged in development of bottom-up syntheses of various materials under mild conditions. Ansocalcin, a protein isolated from goose eggshell matrix, induces the construction of spherical calcite polycrystalline aggregates (6). Osteopontin, a protein that is abundant in urine, interacts with the specific crystal edges of calcium oxalate and influences the morphology of the crystals (7).…”