Flexibility in Mannan-Binding Lectin-Associated Serine Proteases-1 and -2 Provides Insight on Lectin Pathway Activation.
Flexibility in Mannan-Binding Lectin-Associated Serine Proteases-1 and -2 Provides Insight on Lectin Pathway Activation.
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DOI：
10.1016/j.str.2016.12.014
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发表时间：
2017-02-07
期刊：
影响因子：
--
通讯作者：
Perkins SJ
中科院分区：
文献类型：
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作者：
Nan R;Furze CM;Wright DW;Gor J;Wallis R;Perkins SJ
补体的凝集素途径是由识别成分(甘露糖结合凝集素、血清无花果蛋白、胶凝素-LK或胶凝素-K1)和丝氨酸蛋白酶(MASP-1或MASP-2)组成的复合体激活的。MASP-1激活MASP-2，MASP-2裂解C4和C4b结合的C2。为了阐明活性，通过X射线散射、分析超速离心法和原子模拟确定了结合钙离子的MASP二聚体的新晶体结构和溶液结构。每个MASP的CuB1-EGF-CuB2二聚体的溶液结构表明，两个CuB2结构域与晶体结构相比倾斜了90°，表明在EGF-CuB2结合处有相当大的柔性。全长MASP二聚体的酶原和活化形式的溶液结构显示出相似的结构，从晶体结构来看，这些结构比预期的要弯曲得多。我们得出结论，MASP-1和MASP-2在多个位点上是灵活的，这种灵活性可能允许复合体内和复合体间的激活。结合Ca~(2+)的MASP晶体结构揭示了MBL和其他配体的结合部位，MASP晶体结构预测了线性结构域结构，MASP-1和MASP-2的溶液结构从线性方向弯曲了90°，MASP二聚体的灵活性可能允许配合物内和络合物间的活化Nan等人。研究表明，负责启动补体激活的凝集素途径的丝氨酸蛋白酶在溶液中比之前认为的要灵活得多。当甘露聚糖结合的凝集素-MASP复合体结合到病原体表面时，这种灵活性可能促进了复合体内和复合体间的激活。
The lectin pathway of complement is activated by complexes comprising a recognition component (mannose-binding lectin, serum ficolins, collectin-LK or collectin-K1) and a serine protease (MASP-1 or MASP-2). MASP-1 activates MASP-2, and MASP-2 cleaves C4 and C4b-bound C2. To clarify activation, new crystal structures of Ca2+-bound MASP dimers were determined, together with their solution structures from X-ray scattering, analytical ultracentrifugation, and atomistic modeling. Solution structures of the CUB1-EGF-CUB2 dimer of each MASP indicate that the two CUB2 domains were tilted by as much as 90° compared with the crystal structures, indicating considerable flexibility at the EGF-CUB2 junction. Solution structures of the full-length MASP dimers in their zymogen and activated forms revealed similar structures that were much more bent than anticipated from crystal structures. We conclude that MASP-1 and MASP-2 are flexible at multiple sites and that this flexibility may permit both intra- and inter-complex activation. Ca2+-bound MASP crystal structures reveal binding sites for MBL and other ligands The MASP crystal structures predict linear domain structures Solution structures of MASP-1 and MASP-2 are bent by as much as 90° from linearity Flexibility in MASP dimers may permit both intra- and inter-complex activation Nan et al. show that MASPs, the serine proteases responsible for initiating the lectin pathway of complement activation, are much more flexible in solution than previously thought. This flexibility probably facilitates both intra- and inter-complex activation when mannan-binding lectin-MASP complexes bind to pathogen surfaces.