Zhang J H, Stobb J W, Hanesworth J M, Sardinia M F, Harding J W
Department of Veterinary and Comparative Anatomy, Physiology and Pharmacology, Washington State University, Pullman, Washington, USA.
J Pharmacol Exp Ther. 1998 Oct;287(1):416-24.
The Ang IV receptor, AT4, has been shown to play important roles in various mammalian tissues. In this study, structural properties of the AT4 receptor from bovine adrenals are described using a novel photoactive analog of Ang IV, [125I]Benzoylphenylalanine-Ang IV (BP-Ang IV), recently developed in our laboratory. [125I]BP-Ang IV is identical to Ang IV with regards to binding specificity and affinity and is easily cross-linked to the AT4 receptor under UV light, thus greatly facilitating the structural analysis of the AT4 receptor by SDS-PAGE. Comparisons between the native, reduced and nonreduced forms of the AT4 receptors by SDS-PAGE revealed that this receptor consists of multiple subunits. The subunit containing the Ang IV binding site (designated as the alpha subunit) has a molecular weight of approximately 165 kDa and contained approximately 20% N-linked carbohydrates. A subunit similar to the adrenal alpha subunit of the AT4 receptor was identified in all of the bovine tissues examined. Hippocampus and aorta contained additional [125I]BP-Ang IV bound protein bands with molecular weights of 150 and 125 kDa, respectively. Further, the alpha subunit was purified to homogeneity using a method that integrates electrofractionation with conventional protein purification techniques.
血管紧张素IV受体（AT4）已被证明在多种哺乳动物组织中发挥重要作用。在本研究中，我们使用一种新开发的血管紧张素IV光活性类似物[125I]苯甲酰苯丙氨酸 - 血管紧张素IV（BP - Ang IV）描述了牛肾上腺AT4受体的结构特性。[125I]BP - Ang IV在结合特异性和亲和力方面与血管紧张素IV相同，并且在紫外光下很容易与AT4受体交联，从而极大地促进了通过SDS - PAGE对AT4受体的结构分析。通过SDS - PAGE对AT4受体的天然、还原和非还原形式进行比较，发现该受体由多个亚基组成。含有血管紧张素IV结合位点的亚基（称为α亚基）分子量约为165 kDa，含有约20%的N - 连接碳水化合物。在所有检测的牛组织中都鉴定出了一个与AT4受体的肾上腺α亚基相似的亚基。海马体和主动脉分别含有分子量为150 kDa和125 kDa的额外[125I]BP - Ang IV结合蛋白条带。此外，使用一种将电分级分离与传统蛋白质纯化技术相结合的方法将α亚基纯化至同质。
