Molecular determinants of calcitic biomineralization

方解石生物矿化的可重复性导致鸟类蛋壳精确定义的结构特征，这继续引起生物科学家的兴趣和社会的关注。鸡蛋壳制造中的缺陷是人类健康和食品安全问题。在加拿大，每年约有1万例沙门氏菌中毒是由于蛋壳破裂造成的。鸟类蛋壳是已知最快的钙化过程之一;在鸡蛋的日常形成过程中，6克矿物质在不到20小时内沉积在蛋壳膜表面。在过去的15年里，我的NSERC研究计划已经确定了蛋壳基质中调节碳酸钙晶体成核和生长的蛋白质成分。尽管取得了这些进展，但调节钙化的初始和终末阶段的机制和分子还没有很好地理解。 此外，无定形碳酸钙（ACC）越来越多地被认为是生物钙化中方解石的非结晶前体，但对其在蛋壳矿化中的可能作用仍知之甚少。 具体说明：A. 确定纯化的Ovocleidin-17是否催化ACC转化为方解石，以及ACC是否在体内发生并在蛋壳矿化中起作用; B. 鉴定和表征与调节钙化的膜和乳头锥处矿化起始相关的蛋白质; C. 表征蛋壳外层的蛋白质组，并研究Ovocalyxin-32等成分对抑制方解石形成的影响。 对加拿大的意义： 食品安全是鸡蛋的一个重要问题;在加拿大，每年约有10，000起沙门氏菌中毒事件是由蛋壳破裂造成的。 确定蛋壳矿化的新机制（通过ACC）和特定蛋白质（即OC-17，OCX-32）的新作用将导致壳强度和消费者安全性的改善。

The reproducible nature of calcitic biomineralization that results in the precisely defined structural features of the avian eggshell continues to intrigue biological scientists and to concern society. Flaws in chicken eggshell fabrication are a human health and food safety issue. In Canada, about 10,000 annual cases of salmonella poisoning are due to contamination of cracked eggshells. The avian eggshell is one of the fastest calcifying processes known; 6 g of mineral is deposited upon the surface of the eggshell membranes in less than 20 hr during the daily formation of the chicken egg. My NSERC research program during past 15 years has identified protein components of the eggshell matrix that modulate calcium carbonate crystal nucleation and growth. In spite of this progress, the mechanism and molecules that regulate the initial and terminal phases of calcification are not well understood. Moreover, amorphous calcium carbonate (ACC) is increasingly recognized as a non-crystalline precursor to calcite in biological calcification, but there is still very little known about its possible role in eggshell mineralization. SPECIFIC OBJECTIVES: A. Determine whether purified Ovocleidin-17 catalyses the transformation of ACC to calcite, and if ACC occurs in vivo and plays a role in eggshell mineralization; B. Identify and characterize the proteins associated with initiation of mineralization at the membranes and mammillary cones which regulate calcification; C. Characterize the proteome of the outer eggshell , and investigate the impact of constituents such as Ovocalyxin-32 on inhibition of calcite formation. SIGNIFICANCE TO CANADA: Food safety is an important issue for the chicken egg; cracked eggshells are responsible for about 10,000 cases of salmonella poisoning annually in Canada. Identification of a new mechanism for eggshell mineralization (via ACC) and new roles for specific proteins (i.e. OC-17, OCX-32) will lead to improvements in shell strength and safety for the consumer.