Alpers D H, Grimme N, Smith R, Avioli L V
Gastroenterology. 1980 Aug;79(2):259-64.
Dog intestinal mucosa has been found to contain more than one vitamin D-responsive calcium-binding protein (CaBP). Duodenal and upper jejunal mucosa contains a protein that has a mol wt of 19,000 and a Kd of 1.2 microM, and that increases in activity over twofold after administration of 1,25 (OH)2 vitamin D3. This protein could not be demonstrated in ileal tissue. In ileal mucosa all the calcium binding activity resides in fractions that elute from Sephadex G200 with a mol wt of about 57,000. Calcium-binding activity was demonstrated in gel electrophoresis corresponding to a protein with an Rf of about 0.5, unlike the small CaBP, which has an Rf of 1.0. The calcium-binding activity from the ileum was demonstrated to coincide with a protein band on acrylamide gel electrophoresis, and to be destroyed by pronase. This large CaBP responded to 1,25 (OH02 vitamin D3 by increasing activity by about 50%, and was inhibited similarly to the small protein by Sr, Ba, and Mg. Neither fresh tissue homogenates, nor explants cultured up to 20 hr showed any evidence of the small CaBP on disc gel acrylamide electrophoresis. The small CaBP could be demonstrated on gel electrophoresis only in tissue that was partially autolyzed or was treated with a 10% (milligrams per milligram) solution of trypsin. The small CaBP was relatively resistant to trypsin. It is suggested that the small CaBP may be derived at least in part from the large protein.
已发现犬肠道黏膜含有不止一种维生素D反应性钙结合蛋白（CaBP）。十二指肠和空肠上段黏膜含有一种分子量为19,000、解离常数为1.2微摩尔的蛋白质，在给予1,25 - 二羟维生素D3后其活性增加两倍以上。这种蛋白质在回肠组织中未被证实。在回肠黏膜中，所有的钙结合活性都存在于从葡聚糖凝胶G200洗脱的分子量约为57,000的组分中。在凝胶电泳中显示出钙结合活性，对应一种相对迁移率（Rf）约为0.5的蛋白质，这与相对迁移率为1.0的小CaBP不同。回肠的钙结合活性在丙烯酰胺凝胶电泳上与一条蛋白带一致，并被链霉蛋白酶破坏。这种大的CaBP对1,25 - 二羟维生素D3有反应，活性增加约50%，并且与小蛋白类似地受到锶、钡和镁的抑制。无论是新鲜组织匀浆还是培养长达20小时的外植体，在圆盘凝胶丙烯酰胺电泳上都未显示出小CaBP的任何迹象。小CaBP仅在部分自溶或用10%（毫克/毫克）胰蛋白酶溶液处理的组织的凝胶电泳上才能被证实。小CaBP对胰蛋白酶相对抗性较强。有人提出小CaBP可能至少部分源自大蛋白。
