Purification and Characterization of a Calcium Carbonate-Crystal-Growth Inhibitor from Bacterium in Antarctic Lake Vanda(平成16年度 第50回低温生物工学会研究報告)

抄録

A calcium salt crystal controlling bacterium was isolated from the Antarctic Lake Vanda, which contains a high concentration of this calcium compound, and identified as Bacillus sp. based on its taxonomical characteristics. A calcium carbonate-crystal-growth inhibitor (CCGI) from the Antarctic bacterium, and present in cells, strongly inhibits precipitation from supersaturated calcium carbonate solutions. Therefore, we suggest that this new secretor protein may act as an inhibitor of spontaneous calcium carbonate precipitation from supersaturated pancreatic juice. CCGI from an extract of this strain was purified and characterized. We found that the purified CCGI was a monomer of approximately 7,100 according to gel filtration chromatography (Sephacryl S-100) and SDS-PAGE, and was a heat-stable protein. The protein inhibited the crystal growth of calcium carbonate and also affected the crystal morphology. Most of the crystals showed a rhombohedra crystal morphology in the absence of CCGI. On the other hand, CCGI produced different initial morphologies, i.e., the rounded shape for CCGI. These CCGI peptides may interact with different sites of the growing crystals, preventing further accretion of the mineral, thereby changing the crystal morphology.