晶体研究人类血管生成素的c端部分的角色定义酶效价。
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列奥尼达DD,夏皮罗R,苏巴拉奥问,Russo Acharya KR
晶体研究人类血管生成素的c端部分的角色定义酶效价。
生物化学。2002年2月26日,41 (8):2552 - 62。
- PubMed ID
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11851402 (在PubMed]
- 文摘
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人类血管生成素(Ang)在胰核糖核酸酶是一种核糖核酸酶总科,诱导血管生成。其催化活性相对较弱,但生物活性的关键。Ang的晶体结构表明,酶的效力是减毒的阻塞性定位中的Gln117 B(1)嘧啶绑定的口袋,和残留的c端段117 - 123必须调整和绑定和裂开的RNA。本机封闭构象似乎稳定Gln117-Thr44和Asp116-Ser118氢键和疏水包装Ile119 Phe120。符合这一观点,Q117G、D116H I119A / F120A变异比Ang 4-30-fold更加活跃。我们已经确定晶体结构对这些变异检查活动增加的结构基础。在所有三个案例中,c端部分仍然是阻塞性,证明没有残留已经取代了维持封闭的构象是至关重要的。Q117G结构没有变化以外的损失117年残基侧链,而那些D116H和I119A / F120A揭示c端扰动在更换网站之外,表明本机封闭构象一直不稳定。因此,Gln117似乎不那么重要的相互作用比残留的116年,119年和120年的稳定。D116H, His116不复制的氢键Asp116 Ser118而形式与催化残留His114 water-mediated互动; residues 117-121 deviate significantly from their positions in Ang. In I119A/F120A, the segment of residues 117-123 has become highly mobile and all of the interactions thought to position Gln117 have been weakened or lost; the space occupied by Phe120 in Ang is partially filled by Arg101, which has moved several angstroms. A crystal structure was also determined for the deletion mutant des(121-123), which has 10-fold reduced activity toward large substrates. The structure is consistent with the earlier proposal that residues 121-123 form part of a peripheral substrate binding subsite, but also raises the possibility that changes in the position of another residue, Lys82, might be responsible for the decreased activity of this variant.