Low T L, Goldstein A L
J Biol Chem. 1979 Feb 10;254(3):987-95.
The amino acid sequences of two polypeptide components of thymosin Fraction 5 termed thymosin alpha1 and polypeptide beta1 have been established. The sequences were determined by automatic Edman degradation of the intact molecules as well as by manual sequence analysis of the enzymatic cleavage products. Thymosin alpha1, an immunologically active polypeptide, is highly acidic with an isoelectric point of 4.2. This molecule is composed of 28 amino acid residues with acetylserine as the NH2 terminus. A chemically synthesized molecule of thymosin alpha1 has been found to be as active as the natural molecule in our bioassay systems. Polypeptide beta1 is a molecule consisting of 74 amino acid residues and has an isoelectric point of 6.7. This peptide is not biologically active in our assay systems, suggesting that it is not involved in thymic hormone action. The sequence of beta1 was found to be identical with ubiquitin and a portion of protein A24, a nuclear chromosomal protein. The relationships among these proteins are discussed.
已确定了胸腺素5组分的两种多肽成分（称为胸腺素α1和多肽β1）的氨基酸序列。这些序列是通过完整分子的自动埃德曼降解以及酶解产物的手动序列分析来确定的。胸腺素α1是一种具有免疫活性的多肽，高度酸性，等电点为4.2。该分子由28个氨基酸残基组成，以乙酰丝氨酸作为氨基末端。在我们的生物测定系统中，已发现化学合成的胸腺素α1分子与天然分子具有相同的活性。多肽β1是一个由74个氨基酸残基组成的分子，等电点为6.7。该肽在我们的测定系统中无生物活性，这表明它不参与胸腺激素的作用。已发现β1的序列与泛素以及核染色体蛋白A24的一部分相同。讨论了这些蛋白质之间的关系。
