Role of the disulfide cleavage induced molten globule state of type A botulinum neurotoxin in its endopeptidase activity
Role of the disulfide cleavage induced molten globule state of type A botulinum neurotoxin in its endopeptidase activity
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DOI：
10.1021/bi011350g
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发表时间：
2001-12-18
期刊：
影响因子：
2.9
通讯作者：
Singh, BR
中科院分区：
文献类型：
--
作者：
Cai, SW;Singh, BR
肉毒杆菌神经毒素是由厌氧肉毒杆菌以非活性形式产生的。 A 型肉毒杆菌神经毒素 (BoNT/A) 的内肽酶活性是通过还原其重链和轻链之间的二硫键而触发的。通过使用圆二色光谱，我们表明，在 BoNT/A 还原和生理温度（37 ℃）下，BoNT/A 失去其大部分天然三级结构，同时保留其大部分二级结构。这种结构的特点是熔球型构象，这一点通过 1-苯胺萘-8-磺酸的特征结合得到了 BoNT/A 的进一步证实。在链间二硫键完整的非还原条件下，无酶活性的 BoNT/A 不显示熔球类型的结构。 BoNT/A的结构和酶活性的温度分布表明，在还原条件下，熔球结构的存在与约37℃的最佳内肽酶活性存在很强的相关性。
Botulinum neurotoxins are produced by anaerobic Clostridium botulinum in an inactive form. The endopeptidase activity of type A botulinum neurotoxin (BoNT/A) is triggered by reduction of its disulfide bond between its heavy chain and light chain. By using circular dichroism spectroscopy, we show that, upon reduction of BoNT/A and under physiological temperature (37 degreesC), the BoNT/A loses most of its native tertiary structure, while retaining most of its secondary structure. This type of structure is characterized as a molten globule type conformation, which was further confirmed for BoNT/A by the characteristic binding of 1-anilinonaphthalene-8-sulfonic acid. Under nonreducing conditions where the interchain disulfide bond is intact, the enzymatically inactive BoNT/A did not show a molten globule type of structure. A temperature profile of the structure and enzyme activity of BoNT/A revealed that, under reducing conditions, there was a strong correlation in the existence of the molten globule structure and optimum endopeptidase activity at about 37 degreesC.