STRUCTURE OF A CALCIUM-INDEPENDENT PHOSPHOLIPASE-LIKE MYOTOXIC PROTEIN FROM BOTHROPS-ASPER VENOM
STRUCTURE OF A CALCIUM-INDEPENDENT PHOSPHOLIPASE-LIKE MYOTOXIC PROTEIN FROM BOTHROPS-ASPER VENOM
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DOI：
10.1107/s0907444994011455
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发表时间：
1995-05-01
期刊：
影响因子：
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通讯作者：
TULINSKY, A
中科院分区：
文献类型：
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作者：
ARNI, RK;WARD, RJ;TULINSKY, A
肌毒素II是一种肌毒性的钙非依赖性磷脂酶样蛋白，从肉毒杆菌的毒液中分离出来，没有可检测到的磷脂酶活性。在2.8埃下对晶体结构进行了测定和细化，R因子为16.5% (fbbb3sigma)，具有良好的立体化学性质。催化活性磷脂酶和肌毒素LI在Ca2+结合区域的氨基酸差异，特别是Tyr28—b> Asn, Gly32—>Leu和Asp49—>Lys的取代，导致局部构象的改变。关键的区别在于Lys49的ε -氨基填充了催化活性磷脂酶中通常由钙离子占据的位置。与来自鱼尾蝮蛇的同源单体Lys49变体相比，肌毒素II在溶液和晶体状态下都以二聚体的形式存在。不对称单元中的两个分子由几乎完美的双轴相连，但二聚体与Crotalus atrox磷脂酶形成的二聚体截然不同。在肌毒素II中，二聚体界面封闭活性位点，而在肌毒素II中，它们暴露于溶剂中。
Myotoxin II, a myotoxic calcium-independent phospholipase-like protein isolated from the venom of Bothrops asper, possesses no detectable phospholipase activity. The crystal structure has been determined and refined at 2.8 Angstrom to an R factor of 16.5% (F>3 sigma) with excellent stereochemistry. Amino-acid differences between catalytically active phospholipases and myotoxin LI in the Ca2+-binding region, specifically the substitutions Tyr28-->Asn, Gly32-->Leu and Asp49-->Lys, result in an altered local conformation. The key difference is that the epsilon-amino group of Lys49 fills the site normally occupied by the calcium ion in catalytically active phospholipases. In contrast to the homologous monomeric Lys49 variant from Agkistrodon piscivorus piscivorus, myotoxin II is present as a dimer both in solution and in the crystalline state. The two molecules in the asymmetric unit are related by a nearly perfect twofold axis, yet the dimer is radically different from the dimer formed by the phospholipase from Crotalus atrox. Whereas in C. atrox the dimer interface occludes the active sites, in myotoxin II they are exposed to solvent.