DIFFERENCES IN NATURE OF INTERACTION OF INSULIN AND PROINSULIN WITH ZINC
DIFFERENCES IN NATURE OF INTERACTION OF INSULIN AND PROINSULIN WITH ZINC
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DOI：
10.1042/bj1260433
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发表时间：
1972-01-01
影响因子：
4.1
通讯作者：
COOMBS, TL
中科院分区：
文献类型：
--
作者：
GRANT, PT;FRANK, BH;COOMBS, TL
1.本文用平衡透析（超滤）、超滤沉降平衡和速度测定法研究了锌与猪胰岛素和胰岛素原在pH 7时的可逆相互作用。从平衡计算的结合值，其中游离锌与结合锌的比率在0.01：1-10：1的范围内变化，表明胰岛素原和胰岛素各自含有两个主要的锌结合顺序，对金属具有非常不同的亲和力。2.在含有低浓度游离锌的平衡中（游离：结合比为0.01-0.1：1），胰岛素和胰岛素原聚集形成可溶性六聚体，其中含有牢固结合的锌（高达0.284 g-原子/单体），表观固有缔合常数为1.9× 106 m −1。3.较高浓度的锌（游离：结合比为0.1-10.0：1）导致胰岛素和胰岛素原的金属络合物的锌结合、聚集和溶解度性质的渐进性差异。在游离锌浓度最高时，胰岛素原结合总量超过5.0g-原子/单体，并聚集形成可溶性聚合物的混合物（主要为5.1S）。相比之下，胰岛素结合的总量仅为1. 0 g-原子/单体，并且几乎完全从溶液中沉淀出来。4.这些结果表明，在胰岛素原中连接胰岛素部分的肽段的存在并不阻止锌与胰岛素部分的牢固结合和锌-胰岛素原六聚体的形成。同时，尽管连接肽含有对锌具有较低亲和力的额外位点，其应促进分子间和分子内交联，但锌-胰岛素原六聚体的一般构象必须排除在平衡时不溶于溶液的非常大且紧密堆积的聚集体的形成。
1. The reversible interaction of zinc with pig insulin and proinsulin has been studied at pH7 by equilibrium dialysis (ultrafiltration) and by sedimentation equilibrium and velocity measurements in the ultracentrifuge. Binding values calculated from equilibria, where the ratio of free to bound zinc was varied in the range 0.01:1–10:1, indicated that proinsulin and insulin each contained two main orders of zinc binding with very different affinities for the metal. 2. In equilibria containing low concentrations of free zinc (free: bound ratios of 0.01–0.1:1) both insulin and proinsulin aggregated to form soluble hexamers containing firmly bound zinc (up to 0.284g-atom/monomer) with an apparent intrinsic association constant of 1.9×106m−1. 3. Higher concentrations of zinc (free: bound ratios of 0.1–10.0:1) resulted in a progressive difference in the zinc binding, aggregation and solubility properties of the metal complexes of insulin and proinsulin. At the highest concentration of free zinc, proinsulin bound a total of more than 5.0g-atom/monomer and aggregated to form a mixture of soluble polymers (mainly 5.1S). In contrast, insulin bound a total of only 1.0g-atom/monomer and was almost completely precipitated from solution. 4. These results would indicate that the presence of the peptide segment connecting the insulin moiety in proinsulin does not prevent the firm binding of zinc to the insulin moiety and the formation of hexamers of zinc–proinsulin. At the same time although the connecting peptide contains additional sites of lower affinity for zinc, which should facilitate inter- and intra-molecular cross-linking, the general conformation of the zinc–proinsulin hexamer must preclude the formation of very large and close-packed aggregates that are insoluble in solutions at equilibrium.