Mirmira R G, Tager H S
Department of Biochemistry and Molecular Biology, University of Chicago, Illinois 60637.
Biochemistry. 1991 Aug 20;30(33):8222-9. doi: 10.1021/bi00247a019.
By the semisynthesis of both full-length insulin analogues and their des-pentapeptide-(B26-B30)-alpha-carboxamide counterparts, we have examined the importance of the electronic character and bulk of the position B25 side chain both in directing insulin interaction with its receptor on isolated canine hepatocytes and in determining the ability of insulin to self-associate in solution. Analogues include those in which PheB25 was replaced by cyclohexyl-Ala; Tyr; p-nitro-, p-fluoro-, p-iodo-, or p-amino-Phe; or p-amino-Phe in which the aromatic amino function had been acylated by the acetyl, hexanoyl, decanoyl, or 1-adamantanoyl group. Our findings identify that (a) the beta-aromatic side chain at position B25 is indeed critical for high-affinity ligand-receptor interactions, (b) neither electron withdrawal from nor electron donation to the beta-aromatic ring perturbs ligand-receptor interactions in major ways, (c) considerable latitude is allowed the placement of linear or polycyclic apolar mass at the para position in p-amino-PheB25-substituted analogues with respect both to receptor binding affinity and to biological activity in vivo, and (d) para apolar mass at position B25 is readily accommodated during the self-association of insulin monomers, as assessed by analytical tyrosine radioiodination and spectroscopic analysis of analogue complexes with Co2+ and Co3+. These findings are discussed in terms of a model for insulin-receptor interactions at the cell membrane in which the position B25 side chain defines the edge of intermolecular contact.
通过对全长胰岛素类似物及其去五肽 -（B26 - B30）-α-羧酰胺对应物的半合成，我们研究了B25位侧链的电子特性和体积在指导胰岛素与分离的犬肝细胞上的受体相互作用以及确定胰岛素在溶液中自缔合能力方面的重要性。类似物包括用环己基 - 丙氨酸、酪氨酸、对硝基 -、对氟 -、对碘 - 或对氨基 - 苯丙氨酸取代苯丙氨酸B25的那些，或者是其芳香氨基功能已被乙酰基、己酰基、癸酰基或1 - 金刚烷基酰化的对氨基 - 苯丙氨酸。我们的研究结果表明：（a）B25位的β-芳香侧链对于高亲和力配体 - 受体相互作用确实至关重要；（b）无论是从β-芳香环吸电子还是给电子，都不会以主要方式干扰配体 - 受体相互作用；（c）对于对氨基 - 苯丙氨酸B25取代类似物中对位线性或多环非极性基团的放置，在受体结合亲和力和体内生物活性方面都有相当大的自由度；（d）通过分析酪氨酸放射性碘化以及与Co2 +和Co3 +的类似物复合物的光谱分析评估，B25位的对位非极性基团在胰岛素单体自缔合过程中很容易被容纳。根据细胞膜上胰岛素 - 受体相互作用的模型对这些发现进行了讨论，其中B25位侧链定义了分子间接触的边缘。
