Bhattacharyya B, Wolff J
Proc Natl Acad Sci U S A. 1976 Jul;73(7):2375-8. doi: 10.1073/pnas.73.7.2375.
Rat brain tubulin possesses two distinct binding sites for vinblastine per molecule: a high-affinity site with an affinity constant of 6.2 x 10(6) M-1 and a low-affinity site with an affinity constant of 8 x 10(4) M-1. The high-affinity site is labile, with a t1/237 degrees of 3.5 hr, is protected by colchicine, and is unaffected by salt, whereas the low-affinity site is stable but is inhibited by salt. Binding to both sites is rapid. The high-affinity binding constant of vinblastine to tubulin (6.2 x 10(6) M-1) corresponds to the half-maximal concentration of vinblastine needed to prevent polymerization of tubulin in vitro, whereas the low-affinity binding constant (8 x 10(4) M-1) corresponds to the half-maximal concentration of vinblastine required to aggregate tubulin. We conclude that vinblastine binding to the high- and low-affinity sites, respectively, accounts for the depolymerization and aggregation behavior of tubulin.
一个高亲和力位点,亲和常数为6.2×10⁶ M⁻¹,一个低亲和力位点,亲和常数为8×10⁴ M⁻¹。高亲和力位点不稳定,37℃时的半衰期为3.5小时,受秋水仙碱保护,不受盐的影响,而低亲和力位点稳定但受盐抑制。与两个位点的结合都很快。长春花碱与微管蛋白的高亲和力结合常数(6.2×10⁶ M⁻¹)对应于体外防止微管蛋白聚合所需的长春花碱半最大浓度,而低亲和力结合常数(8×10⁴ M⁻¹)对应于聚集微管蛋白所需的长春花碱半最大浓度。我们得出结论,长春花碱分别与高亲和力和低亲和力位点的结合解释了微管蛋白的解聚和聚集行为。