Assembly and disassembly kinetics of anthrax toxin complexes
Assembly and disassembly kinetics of anthrax toxin complexes
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DOI：
10.1021/bi051830y
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发表时间：
2006-02-21
期刊：
影响因子：
2.9
通讯作者：
Collier, RJ
中科院分区：
文献类型：
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作者：
Christensen, KA;Krantz, BA;Collier, RJ
炭疽毒素的保护性抗原（PA）组分的蛋白水解活化使其自缔合成环状同源七聚体[PA（63）]（7），其可以结合酶组分致死因子（LF）和水肿因子（EF）。[PA（63）]（7）是一种孔前体（prepore），在内体的低pH条件下，它形成一个允许LF和EF进入胞质溶胶的跨膜孔。用供体和受体荧光染料标记PA，并用Forster共振能量转移法测定了前孔复合物在溶液中的组装和分解动力学。[PA（63）]（7）的解离速率常数为1 × 10（-6）s（-1）（t（1/2）类似于7天）。相反，含有LF（LFN）的PA结合结构域的三元复合物与PA（63）二聚体结合，PA（63）二聚体由两个非寡聚突变体组成，三元复合物迅速解离（t（1/2）类似于1 min）。因此，相对于三元复合物，[PA（63）]（7）的分解速率的显著降低是由于七聚体环中相邻亚基之间的协同相互作用。低浓度的LFN促进组装的prepore从蛋白水解激活PA，而高浓度抑制组装的prepore和三元复合物。提出了一种炭疽毒素复合物的自组装方案。
Proteolytic activation of the protective antigen (PA) component of anthrax toxin allows it to self-associate into a ring-shaped homoheptamer, [PA(63)](7), which can bind the enzymatic components lethal factor (LF) and edema factor (EF). [PA(63)](7) is a pore-precursor (prepore), and under the low-PH conditions of the endosome, it forms a transmembrane pore that allows LF and EF to enter the cytosol. PA was labeled with donor and acceptor fluorescent dyes, and Forster resonance energy transfer was used to measure the assembly and disassembly kinetics of the prepore complex in solution. The dissociation rate constant for [PA(63)](7) was 1 X 10(-6) s(-1) (t(1/2) similar to 7 days). In contrast, a ternary complex containing the PA-binding domain of LF (LFN) bound to a PA(63) dimer composed of two nonoligomerizing mutants dissociated rapidly (t(1/2) similar to 1 min). Thus, the substantial decrease in the rate of disassembly of [PA(63)](7) relative to the ternary complex is due to the cooperative interactions among neighboring subunits in the heptameric ring. Low concentrations of LFN promoted assembly of the prepore from proteolytically activated PA, whereas high concentrations inhibited assembly of both the prepore and the ternary complex. A self-assembly scheme of anthrax toxin complexes is proposed.