Study on microbial proteiolipid involved in haydroxyapatite formation.

Matruchotii棒状杆菌是从牙石中分离到的一种参与牙石形成的微生物，主要由羟基磷灰石组成。该菌对分析钙化过程的机理具有重要意义。我们从氯仿：甲醇脂提取物中提纯了能够结合8个钙离子分子的蛋白脂(Ca^&lt；2&gt；)，很可能是这种蛋白脂最初与该蛋白脂结合促进了无机磷酸盐的结合，最终形成了羟基磷灰石。将编码该蛋白脂基因的DNA片段(CplX)插入p-BAD载体中，并将其导入大肠杆菌。在大肠杆菌中成功表达了CplX蛋白，但重组蛋白没有钙化。甲醇KOH去除共价连接的酰基部分会降低其形成钙磷脂的能力。分析CplX在松材线虫和大肠杆菌中的酰化位点的差异，对于进一步研究其钙化过程具有重要意义。

Corynebacterium matruchotii is a microbe isolated from dental calculus and involved in the calculus formation mainly composed of hydroxyapatite. This microbe is very important for analyzing mechanism of the calcification process. We have purified proteolipid capable of binding eight molecules of calcium ion (Ca^<2+>) from chloroform : methanol lipid extracts It is likely that the initial binding of Ca^<2+> with this proteolipid promotes inorganic phosphate association and eventually hydroxyapatite formation. A PCR-amplified DNA fragment encoding this proteolipid gene (cplX) was inserted into a p-BAD plasmid and then introduced into Escherichia coli. The CplX protein was successfully expressed in E.coli, but the recombinant was not calcified. Removal of covalently attached acyl moieties by methanolic KOH decreased its ability to form Ca-phospholipid. To analyze the differences in acylation sites of CplX in C.matruchotii and E.coli would be very important for further study of the calcification process.