Study on microbial proteiolipid involved in haydroxyapatite formation.

matruchoti棒状杆菌是一种从牙结石中分离出来的微生物，参与主要由羟基磷灰石组成的牙结石的形成。这种微生物对钙化过程机理的分析具有重要意义。我们从氯仿：甲醇脂质提取物中纯化了能够结合8个钙离子分子（Ca^<2+>）的蛋白脂。很可能Ca^<2+>与这种蛋白脂的初始结合促进了无机磷酸盐的结合，最终形成羟基磷灰石。将pcr扩增的编码该蛋白脂基因（cplX）的DNA片段插入p-BAD质粒中，然后导入大肠杆菌。CplX蛋白在大肠杆菌中成功表达，但重组蛋白未发生钙化。甲醇KOH去除共价连接的酰基部分降低了其形成钙磷脂的能力。分析马氏杆菌和大肠杆菌中CplX酰化位点的差异，对进一步研究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.