A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin.
A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin.
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DOI：
10.3390/toxins7072674
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发表时间：
2015-07-20
期刊：
影响因子：
4.2
通讯作者：
Teter K
中科院分区：
文献类型：
--
作者：
Taylor M;Curtis D;Teter K
霍乱毒素(CT)由催化A1亚基、A2连接子和同膜细胞结合B亚基组成。完整的全毒素通过囊泡载体从细胞表面移动到内质网(ER)，在那里CTA1从其余的毒素中释放出来。然后，解离的CTA1亚基转变为未折叠的构象，这触发了它通过涉及内质网相关降解的质量控制系统(ERAD)的过程输出到细胞质中。我们假设，分离的CTA1的展开将阻止其与CTA2/CTB5的非生产性重新结合。为了验证这一预测，我们通过表面等离子体共振监测了CTA1与CTA2/CTB5的实时重新结合。折叠的而非无序的CTA1可与CTA2/CTB5相互作用，形成稳定的功能性全毒素。因此，我们的数据确定了分离的CTA1多肽在宿主-毒素相互作用中的内在不稳定性的另一个作用：除了激活ERAD易位机制外，游离CTA1在37℃的自发展开阻止了CT全毒素在内质网中的非生产性重组。
Cholera toxin (CT) consists of a catalytic A1 subunit, an A2 linker, and a homopentameric cell-binding B subunit. The intact holotoxin moves by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) where CTA1 is released from the rest of the toxin. The dissociated CTA1 subunit then shifts to an unfolded conformation, which triggers its export to the cytosol by a process involving the quality control system of ER-associated degradation (ERAD). We hypothesized that the unfolding of dissociated CTA1 would prevent its non-productive reassociation with CTA2/CTB5. To test this prediction, we monitored the real-time reassociation of CTA1 with CTA2/CTB5 by surface plasmon resonance. Folded but not disordered CTA1 could interact with CTA2/CTB5 to form a stable, functional holotoxin. Our data, thus, identified another role for the intrinsic instability of the isolated CTA1 polypeptide in host-toxin interactions: in addition to activating the ERAD translocation mechanism, the spontaneous unfolding of free CTA1 at 37 °C prevents the non-productive reassembly of a CT holotoxin in the ER.