Silvestri L, Baker J R, Rodén L, Stroud R M
J Biol Chem. 1981 Jul 25;256(14):7383-7.
An inhibitor of human C1q has been purified from serum and identified as a chondroitin 4-sulfate proteoglycan. A typical preparation contained 22% uronic acid, 20% hexosamine, 12% sulfate, and 9% protein. When chromatographed on Sepharose CL-2B, the proteoglycan was eluted as a broad peak with a mean Kav of 0.6, which indicates that it is polydisperse and has an average Mr = approximately 175,000 (range, 45,000-750,000). Unlike the major species of cartilage proteoglycans, the serum proteoglycan did not form a complex with hyaluronic acid. Additional evidence for the noncartilaginous origin of C1q inhibitor is that its glycosaminoglycan chains totally lack chondroitin 6-sulfate isomers. Furthermore, the glycosaminoglycan component of C1q inhibitor was eluted from Sepharose CL-6B with a Kav of 0.52, indicating that these polysaccharide chains are considerably larger than those of human articular cartilage proteoglycan. The interaction between the proteoglycan and C1q was clearly evident in 0.15 M NaCl, as demonstrated by a radial immunodiffusion technique. The interaction decreased with increasing ionic strength but was not entirely abolished even at 0.3 M NaCl. These findings suggest that the interaction between C1q and the C1q inhibitor may occur under physiological conditions and may be of importance in modulating C1q activity in vivo.
一种人C1q抑制剂已从血清中纯化出来，并被鉴定为硫酸软骨素4-硫酸酯蛋白聚糖。典型的制剂含有22%的糖醛酸、20%的己糖胺、12%的硫酸盐和9%的蛋白质。当在琼脂糖CL-2B上进行色谱分析时，蛋白聚糖以一个宽峰形式洗脱，平均Kav为0.6，这表明它是多分散的，平均相对分子质量约为175,000（范围为45,000 - 750,000）。与软骨蛋白聚糖的主要种类不同，血清蛋白聚糖不与透明质酸形成复合物。C1q抑制剂非软骨来源的额外证据是其糖胺聚糖链完全缺乏硫酸软骨素6-硫酸酯异构体。此外，C1q抑制剂的糖胺聚糖成分从琼脂糖CL-6B上洗脱时的Kav为0.52，这表明这些多糖链比人关节软骨蛋白聚糖的多糖链大得多。通过放射免疫扩散技术证明，在0.15M NaCl中蛋白聚糖与C1q之间的相互作用明显。随着离子强度增加，这种相互作用减弱，但即使在0.3M NaCl时也没有完全消除。这些发现表明，C1q与C1q抑制剂之间的相互作用可能在生理条件下发生，并且可能在体内调节C1q活性方面具有重要意义。
