Carraway R E, Mitra S P, Cochrane D E
J Biol Chem. 1987 May 5;262(13):5968-73.
Using a radioimmunoassay toward the COOH-terminal region of neurotensin, an immunoreactive and biologically active neurotensin-related peptide (NRP) has been isolated from pepsin-treated fractions of bovine, canine, human, and rat plasma. Bovine NRP was identified as H-Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe-Leu-OH, which is similar in structure to both neurotensin and angiotensin I. Canine and human NRP also had the above amino acid composition, whereas that obtained from rat plasma had valine substituted for isoleucine. At their concentrations in pepsin-treated plasmas (2-6 microM) rat, human and canine NRP were shown to increase vascular permeability when injected intradermally into rats and to release histamine from rat mast cells in vitro. The pure peptides also cross-reacted very effectively at nanomolar concentrations in a radioreceptor assay for neurotensin. The protein(s) which liberated NRP upon pepsin treatment were purified about 7-fold and shown to behave like albumin during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, and high pressure liquid chromatography on muBondapak C4. In addition, the purified preparations were found to react with anti-albumin antisera during immunodiffusion. Although the amino acid sequence of NRP was not found in albumin, a partial sequence homology was noted for NRP and various segments of bovine albumin. Using V8 protease, glutamyl residues were shown to lie within 3-4 amino acids of each end of NRP, as also occurs for the related segments in albumin. These results suggest that a subset of albumin-related protein(s) could serve as precursor(s) to biologically active neurotensin-related peptide(s).
利用针对神经降压素COOH末端区域的放射免疫分析法，从经胃蛋白酶处理的牛、犬、人及大鼠血浆组分中分离出了一种具有免疫反应性和生物活性的神经降压素相关肽（NRP）。牛NRP被鉴定为H-Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe-Leu-OH，其结构与神经降压素和血管紧张素I均相似。犬和人NRP也具有上述氨基酸组成，而从大鼠血浆中获得的NRP则是缬氨酸取代了异亮氨酸。当大鼠皮内注射大鼠、人及犬的NRP（在经胃蛋白酶处理的血浆中的浓度为2 - 6 microM）时，显示可增加血管通透性，并能在体外从大鼠肥大细胞中释放组胺。在针对神经降压素的放射受体分析中，这些纯肽在纳摩尔浓度下也能非常有效地发生交叉反应。经胃蛋白酶处理后释放NRP的蛋白质被纯化了约7倍，并且在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、等电聚焦以及在μBondapak C4上进行的高压液相色谱分析中表现得类似于白蛋白。此外，在免疫扩散过程中发现纯化制剂与抗白蛋白抗血清发生反应。虽然在白蛋白中未发现NRP的氨基酸序列，但注意到NRP与牛白蛋白的各个片段存在部分序列同源性。使用V8蛋白酶显示，谷氨酰残基位于NRP两端各3 - 4个氨基酸范围内，白蛋白的相关片段也如此。这些结果表明，与白蛋白相关的一部分蛋白质可能是生物活性神经降压素相关肽的前体。
