Chopra R K, Bowness J M
Can J Biochem. 1981 Mar;59(3):191-201. doi: 10.1139/o81-027.
Two noncollagenous insoluble structural glycoprotein fractions (A and G), from uncalcified canine puppy rib cartilage, each contained about 8% of extractable lipid. This percentage of lipid is higher than that found in any of the other tissue fractions obtained by the preparative procedure used. The composition of the lipid extracted from the structural glycoproteins is quite distinct from the lipid in the guanidine . HCl extract of cartilage, the lipid of cartilage matrix vesicles, and that of other known lipid membranes. On ultracentrifugation, solubilized A or G, obtained by using 50 mM dithiothreitol (DTT) in 5 M guanidine . HCl followed by dialysis, showed a floating fraction (density 1.14 - 1.16 g/mL) which was decreased by prior delipidation and increased by lipidation. Chromatography of [3H]palmitate, [14C]cholesterol, or [14C]phosphatidylcholine on Sepharose 2B showed that their elution behaviour is altered in the presence of solubilized A or G. All the labelled lipids cochromatograph, but only with A or G protein in the high molecular weight region. After boiling the low density ultracentrifugation fraction with 1% sodium dodecyl sulfate (SDS), 8 M urea, and 50 mM DTT, disc gel electrophoresis showed that it contained the same subunits as the high density fraction. It is concluded that lipids can readily form a complex with a specific fraction of A or G. This fraction may be a combination of several undissociated subunits or an undenatured form of proteins. The complex is stable enough to be of possible significance in the metabolism of connective tissues. No antigenic relationships have been found between the cartilage structural glycoproteins or cartilage extracts and the plasma lipoproteins LDL, VLDL, and Lp(a).
从未钙化的幼犬犬肋软骨中提取的两种非胶原不溶性结构糖蛋白组分（A和G），每种都含有约8%的可提取脂质。该脂质百分比高于通过所用制备程序获得的任何其他组织组分中的脂质百分比。从结构糖蛋白中提取的脂质组成与软骨的胍盐酸提取物、软骨基质小泡的脂质以及其他已知脂质膜中的脂质截然不同。超速离心时，通过在5M胍盐酸中使用50mM二硫苏糖醇（DTT）然后透析获得的溶解的A或G，显示出一个漂浮组分（密度1.14 - 1.16 g/mL），该组分在预先脱脂时减少，在脂质化时增加。在琼脂糖2B上对[3H]棕榈酸、[14C]胆固醇或[14C]磷脂酰胆碱进行色谱分析表明，在存在溶解的A或G的情况下，它们的洗脱行为会发生改变。所有标记的脂质都一起色谱分离，但仅在高分子量区域与A或G蛋白一起。用1%十二烷基硫酸钠（SDS）、8M尿素和50mM DTT煮沸低密度超速离心组分后，圆盘凝胶电泳显示它含有与高密度组分相同的亚基。得出的结论是，脂质可以很容易地与A或G的特定组分形成复合物。该组分可能是几个未解离亚基的组合或蛋白质的未变性形式。该复合物足够稳定，可能在结缔组织的代谢中具有重要意义。在软骨结构糖蛋白或软骨提取物与血浆脂蛋白LDL、VLDL和Lp(a)之间未发现抗原关系。
