Zumstein P P, Lüthi C, Humbel R E
Proc Natl Acad Sci U S A. 1985 May;82(10):3169-72. doi: 10.1073/pnas.82.10.3169.
Human serum contains, in addition to the "classical" 7.5-kDa insulin-like growth factors (IGFs) I and II, small amounts of larger IGF-II. A 10-kDa IGF-II was isolated by gel filtration, immunoaffinity chromatography, and reversed-phase HPLC. Upon amino acid sequence determination, a substitution of Cys-Gly-Asp for Ser-33 was found as well as a COOH-terminal extension of 21 residues (E peptide). These sequence differences suggest that 10-kDa IGF-II is a precursor of a variant IGF-II. Since the substitution is not located at a known intron/exon hinge region, the finding of this variant IGF-II is evidence for the presence of more than one gene for IGF-II.
除了“经典的”7.5 kDa胰岛素样生长因子(IGF)I和II外,人血清中还含有少量较大的IGF-II。通过凝胶过滤、免疫亲和色谱和反相高效液相色谱分离出了一种10 kDa的IGF-II。在确定氨基酸序列时,发现第33位的丝氨酸被半胱氨酸-甘氨酸-天冬氨酸取代,并且有一个21个残基的羧基末端延伸(E肽)。这些序列差异表明10 kDa的IGF-II是一种变异型IGF-II的前体。由于该取代不在已知的内含子/外显子铰链区,这种变异型IGF-II的发现证明了IGF-II存在不止一个基因。