Conformational flexibility in the flap domains of ligand-free HIV protease
Conformational flexibility in the flap domains of ligand-free HIV protease
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DOI：
10.1107/s0907444907029125
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发表时间：
2007-08-01
影响因子：
2.2
通讯作者：
Stout, C. David
中科院分区：
文献类型：
--
作者：
Heaslet, Holly;Rosenfeld, Robin;Stout, C. David
报道了野生型HIV蛋白酶（HIV PR）在无底物或抑制剂存在下的两种相关晶体形式的晶体结构，分辨率为1.4和2.15埃。在一种晶体形式中，HIV PR采用“开放”构象，在同二聚体中的翼片尖端之间具有7.7埃的间隔。在另一种晶体形式中，翼片的尖端朝向80 s环“卷曲”，形成跨越局部二重轴的接触。还报道了在不存在底物或抑制剂的情况下HIV PR的六倍突变体的2.3埃分辨率晶体结构。突变型HIV PR是在对强效抑制剂TL-3治疗的反应中进化而来的，相对于野生型酶包含6个点突变（L24 I、M46 I、F53 L、L 63 P、V77 I、V82 A）。在这种结构中，翼片也采用“卷曲”构造，但是是分离的并且不接触。与TL-3结合的载脂蛋白结构的比较表明抑制剂结合诱导的构象变化的程度，其中包括两个折叠相关的皮瓣之间的包装的重组。与其他六个载脂蛋白HIV PR结构的进一步比较表明，“开放”和“卷曲”的构象定义两个不同的家庭在HIV PR。这些构象状态包括铰链运动的残基在任何一端的皮瓣，打开和关闭整个β-环，和平移运动的皮瓣正常的二聚体的两倍轴和相对于80秒循环。交替的构象也需要在皮瓣尖端的β-转弯的变化。这些观察提供了深入了解皮瓣域的可塑性，其运动的性质和它们在结合底物和抑制剂的关键作用。
The crystal structures of wild-type HIV protease (HIV PR) in the absence of substrate or inhibitor in two related crystal forms at 1.4 and 2.15 angstrom resolution are reported. In one crystal form HIV PR adopts an 'open' conformation with a 7.7 angstrom separation between the tips of the flaps in the homodimer. In the other crystal form the tips of the flaps are ` curled' towards the 80s loop, forming contacts across the local twofold axis. The 2.3 angstrom resolution crystal structure of a sixfold mutant of HIV PR in the absence of substrate or inhibitor is also reported. The mutant HIV PR, which evolved in response to treatment with the potent inhibitor TL-3, contains six point mutations relative to the wild-type enzyme (L24I, M46I, F53L, L63P, V77I, V82A). In this structure the flaps also adopt a ` curled' conformation, but are separated and not in contact. Comparison of the apo structures to those with TL-3 bound demonstrates the extent of conformational change induced by inhibitor binding, which includes reorganization of the packing between twofold-related flaps. Further comparison with six other apo HIV PR structures reveals that the ` open' and ` curled' conformations define two distinct families in HIV PR. These conformational states include hinge motion of residues at either end of the flaps, opening and closing the entire beta-loop, and translational motion of the flap normal to the dimer twofold axis and relative to the 80s loop. The alternate conformations also entail changes in the beta-turn at the tip of the flap. These observations provide insight into the plasticity of the flap domains, the nature of their motions and their critical role in binding substrates and inhibitors.