A key functional role for the insulin-like growth factor 1 N-terminal pentapeptide.
A key functional role for the insulin-like growth factor 1 N-terminal pentapeptide.
复制标题
胰岛素样生长因子 1 N 末端五肽的关键功能作用。
作者：
J. Christopher;Bagley;Laszlo Szabo;Peter J. McNAMARA;Marina;Ross;G. L. Francis;F. Ballard;J. Wallace
为了阐明胰岛素样生长因子1（IGF-1）的N-末端与其生物学特性的作用，我们化学合成的类似物的IGF-1从N-末端截短1至5个氨基酸残基。在测量大鼠L 6成肌细胞中蛋白质合成刺激的生物测定中，产生半最大反应所需的浓度为：IGF-1，1 - 3 ng/ml; des-（1）-IGF-1，10 ng/ml; des-（1-2）-IGF-1，1 - 3 ng/ml; des-（1-3）-IGF-1，1.5 ng/ml; des-（1-4）-IGF-1，5.1 ng/ml; des-（1-5）-IGF-1，1200 ng/ml。当测试它们在3 ℃下与125 I-IGF-1竞争结合L 6成肌细胞的能力时，50%竞争所需的浓度为：IGF-1，des-（1）-IGF-1和des-（1-2）-IGF-1，20 ng/ml; des-（1-3）-IGF-1，1 - 4 ng/ml; des-（1-4）-IGF-1，40 ng/ml; des-（1-5）-IGF-1，大于1000 ng/ml。然而，在25摄氏度的受体结合实验结果表明，成肌细胞分泌的结合蛋白选择性的三个最长的肽。通过用L 6成肌细胞条件培养基以及从MDBK细胞条件培养基纯化的结合蛋白进行的结合研究证实了这种解释。在这两种情况下，IGF-1、des-（1）-IGF-1和des-（1-2）-IGF-1竞争示踪剂IGF-1结合的能力比三种较短肽强至少60倍。所获得的结果解释了des-（1-3）-IGF-1和des-（1-4）-IGF-1的效力增加，因为它们的活性不被结合蛋白减弱，并且des-（1-4）-IGF-1的相对较低的效力是该肽与L 6-成肌细胞受体结合不太好的结果。
In order to elucidate the role of the N-terminus of insulin-like growth factor 1 (IGF-1) with respect to its biological properties, we chemically synthesized analogues of IGF-1 truncated by one to five amino acid residues from the N-terminus. In a bioassay that measured the stimulation of protein synthesis in rat L6 myoblasts, the concentrations required to produce a half-maximal response were: IGF-1, 13 ng/ml; des-(1)-IGF-1, 10 ng/ml; des-(1-2)-IGF-1, 13 ng/ml; des-(1-3)-IGF-1, 1.5 ng/ml; des-(1-4)-IGF-1, 5.1 ng/ml; des-(1-5)-IGF-1, 1200 ng/ml. When tested for their abilities to compete with 125I-IGF-1 binding to L6 myoblasts at 3 degrees C, the concentrations required for 50% competition were: IGF-1, des-(1)-IGF-1 and des-(1-2)-IGF-1, 20 ng/ml; des-(1-3)-IGF-1, 14 ng/ml; des-(1-4)-IGF-1, 40 ng/ml; des-(1-5)-IGF-1, greater than 1000 ng/ml. Receptor-binding experiments at 25 degrees C, however, gave results suggesting that the myoblasts were secreting a binding protein selective for the three longest peptides. This interpretation was confirmed by binding studies with medium conditioned by the L6 myoblasts as well as binding protein purified from MDBK-cell-conditioned medium. In both cases IGF-1, des-(1)-IGF-1 and des-(1-2)-IGF-1 competed for tracer IGF-1 binding at least 60-fold better than did the three shorter peptides. The results obtained account for the increased potency of des-(1-3)-IGF-1 and des-(1-4)-IGF-1, since their activities are not attenuated by the binding protein, and the relatively lower potency of des-(1-4)-IGF-1 is a consequence of this peptide binding less well to the L6-myoblast receptor.