Green N M, Toms E J
Biochem J. 1972 Dec;130(3):707-11. doi: 10.1042/bj1300707.
Avidin molecules in which a fraction of the four binding sites were occupied by biotin did not dissociate completely in 6.4m-guanidinium chloride. Only unoccupied subunits dissociated. The remainder recombined to form the tetrameric avidin-biotin complex. The rate at which unoccupied subunits were unfolded and dissociated was only decreased by one-half in species in which three of the four binding sites were occupied by biotin. These results can be explained by assuming that unfolding of unoccupied subunits followed by dissociation from the tetramer is initiated by penetration of guanidinium ions into the binding site and disorganization of this region of the subunit. When a site is occupied by biotin this pathway is blocked and the subunit does not unfold. Each subunit behaves independently and is not markedly stabilized when neighbouring subunits are occupied.
在四个结合位点中有一部分被生物素占据的抗生物素蛋白分子，在6.4M的氯化胍中不会完全解离。只有未被占据的亚基会解离。其余的重新组合形成四聚体抗生物素蛋白-生物素复合物。在四个结合位点中有三个被生物素占据的物种中，未被占据的亚基展开和解离的速率仅降低了一半。这些结果可以通过假设未被占据的亚基先展开然后从四聚体上解离是由胍离子渗透到结合位点并使该亚基区域紊乱来解释。当一个位点被生物素占据时，这条途径就会被阻断，亚基不会展开。每个亚基的行为是独立的，当相邻亚基被占据时，它不会明显稳定。
