兔阑尾中一种新的21kD的钙结合蛋白的纯化与鉴定

纯化与鉴定了Ｂ淋巴细胞中一种新的分子量为２１ｋＤ的钙结合蛋白（ＣａＢＰ２１）。兔阑尾淋巴细胞匀浆经热变性，Ｐｈｅｎｙｌ－Ｓｅｐｈａｒｏｓｅ与ＤＥＡＥ－Ｓｅｐｈａｒｏｓｅ柱层析，自每１ｋｇ细胞沉积物中获得ＳＤＳ－ＰＡＧＥ均一的ＣａＢＰ２１５．３ｍｇ。ＨＣｌ水解后的酸性氨基酸（Ａｓｐ＋Ｇｌｕ）含量为２６％。如同大多数钙结合蛋白一样，Ｎ末端封闭阻止其进行Ｅｄｍａｎ降解。ＣａＢＰ２１中疏水性氨基酸（计Ｇｌｙ，不计Ｔｒｐ）约占４６％，碱性氨基酸１０％，酸性氨基酸与极性氨基酸约４４％。ＣａＢＰ２１有较高的Ｓｅｒ、Ｔｙｒ含量。肽谱分析等确证ＣａＢＰ２１为２个相同或相似亚基二聚体。以ＡｒｓｅｎａｚｏⅢ作Ｃａ２＋结合分析表明每分子ＣａＢＰ２１可结合４分子Ｃａ２＋，对Ｃａ２＋的结合常数约为１０－５ｍｏｌ／Ｌ。各种性质表明ＣａＢＰ２１是一种不同于其他已知钙结合蛋白的新钙结合蛋白。

Purification and Characterization of a Novel 21 kD Calcium binding Protein from Rabbit Appendix Lymphocytes

A novel 21 kD calcium binding protein from rabbit appendix B lymphocytes has been purified and characterized. Through heat denaturation, using Phenyl Sepharose and DEAE Sepharose chromatography, we obtained 5.3 mg SDS PAGE homogeneous CaBP 21 from 1 kg lymphocyte cells. Amino acid analysis showed the acidic amino acid content (asp glu) to be 26% after HCL hydrolysis. The blocking of the N terminus of CaBP 21 prevents the de novo Edman degradation, like most of the other calcium binding proteins. CaBP 21 has 46% of hydrophobic amino acid (with Gly, without Trp) content, 10% of basic amino acid content and 44% of acidic and polar amino acids. Peptide mapping and SDS PAGE combined Sephadex G 25 gel filtration proves that CaBP 21 consists of two identical or similar subunits. Ca 2 binding assays using Arsenazo III indicated one protein to bind 4 Ca 2 with dissociation constant (K d) for Ca 2 about 10 -5 mol/L.