Kage R, Leeman S E, Boyd N D
Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Massachusetts 02118.
J Neurochem. 1993 Jan;60(1):347-51. doi: 10.1111/j.1471-4159.1993.tb05857.x.
Studies were designed to examine the basis for the difference in molecular weights of the two proteins detected in membrane preparations of rat submaxillary glands after photolabeling with a radioactive analogue of substance P, 125I-p-benzoyl-L-phenylalanine8-substance P. When the two proteins were separated and individually digested with endoglycosidase F, the relative molecular weight of each protein was reduced by approximately 10,000, indicating that the extent of glycosylation of both proteins is the same. To test whether the difference in their molecular weights can be attributed to a difference in the lengths of the two proteins, photolabeled membranes were treated with carboxypeptidase Y before solubilization to remove from each photolabeled protein the carboxy-terminal portion that extends beyond the membrane. Only one, albeit diffuse, band was now observed that on subsequent deglycosylation with endoglycosidase F was more clearly seen to be a single band, indicating that differing lengths of peptide chains were cleaved from the two proteins. These results permit the interpretation that the difference in the two forms of the substance P receptor present in rat submaxillary glands is due to differences in the length of their carboxy termini.
研究旨在探究用P物质的放射性类似物125I-p-苯甲酰-L-苯丙氨酸8-P物质进行光标记后，在大鼠下颌下腺膜制剂中检测到的两种蛋白质分子量差异的基础。当将这两种蛋白质分离并用内切糖苷酶F分别消化时，每种蛋白质的相对分子量降低了约10,000，这表明两种蛋白质的糖基化程度相同。为了测试它们分子量的差异是否可归因于两种蛋白质长度的差异，在溶解之前，用光标记的膜用羧肽酶Y处理，以从每个光标记的蛋白质中去除延伸到膜外的羧基末端部分。现在仅观察到一条带，尽管是弥散的，在用内切糖苷酶F进行后续去糖基化后更清楚地看到是一条单带，表明从这两种蛋白质上切割下了不同长度的肽链。这些结果可以解释为，大鼠下颌下腺中存在的两种形式的P物质受体的差异是由于它们羧基末端长度的差异。
