Exchange characteristics of calcium ions bound to anthrax protective antigen
Exchange characteristics of calcium ions bound to anthrax protective antigen
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DOI：
10.1016/s0006-291x(02)02771-7
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发表时间：
2003-01-03
影响因子：
3.1
通讯作者：
Collier, RJ
中科院分区：
文献类型：
--
作者：
Gao-Sheridan, S;Zhang, S;Collier, RJ
保护性抗原（PA）是炭疽毒素的受体结合部分，包含两个埋在域1'内的钙原子（氨基酸残基168-258）。我们表明，这些离子稳定地结合，并与自由CA-45（2+）的交换仅缓慢（t（1/2），类似于4.0 h）。解离是限速步骤。 PA（63），Pa的七聚体前骨形式。与单体完整蛋白相比，汇率略高。通过这种形式的交换是通过毒素的酶促部分的结合来阻碍的，但是不受将pH降低到5.0的影响，pH值为5.0，这是一种已知的疾病，该疾病触发了预卵形转化为孔隙形式。这些结果与以下假设一致：在PA内结合的Ca2+主要是结构性的作用，将域P保持在构象中，该构象使PA（63）能够将毒素的酶基因分离和结合。 （C）2002 Elsevier Science（美国）。版权所有。
Protective antigen (PA), the receptor-binding moiety of anthrax toxin, contains two calcium atoms buried within domain 1' (amino acid residues 168-258). We showed that these ions are stably bound and exchange with free Ca-45(2+) only slowly (t(1/2) similar to 4.0 h). Dissociation is the rate-limiting step. PA(63), the heptameric prepore form of PA. showed a slightly higher exchange rate than the monomeric intact protein. Exchange by this form was retarded by binding of the enzymatic moieties of the toxin, but was unaffected by reducing the pH to 5.0, a condition known to trigger conversion of the prepore to the pore form. These results are consistent with the hypothesis that bound Ca2+ within PA plays primarily a structural role, maintaining domain P in a conformation that allows PA(63) to oligomerize and bind the enzymatic moieties of the toxin. (C) 2002 Elsevier Science (USA). All rights reserved.