The concave face of decorin mediates reversible dimerization and collagen binding.
The concave face of decorin mediates reversible dimerization and collagen binding.
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DOI：
10.1074/jbc.m113.504530
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发表时间：
2013-12-06
期刊：
影响因子：
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通讯作者：
Hohenester E
中科院分区：
文献类型：
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作者：
Islam M;Gor J;Perkins SJ;Ishikawa Y;Bächinger HP;Hohenester E
背景：在核心蛋白聚糖的晶体结构中，两个单体的凹面相互作用形成紧密的二聚体。结果：溶液中的核心蛋白聚糖二聚体与稳定的单体处于平衡状态，凹面上的突变消除了胶原蛋白的结合。结论：核心蛋白聚糖以单体形式结合胶原蛋白。意义：这些发现有助于解决有关核心蛋白聚糖功能性寡聚状态的争议。核心蛋白聚糖是一种典型的富含亮氨酸的小蛋白聚糖，它与胶原蛋白结合，从而调节胶原蛋白组装成原纤维。核心蛋白聚糖核心蛋白的晶体结构揭示了两个单体通过凹面结合形成的紧密二聚体（Scott, P. G.、McEwan, P. A.、Dodd, C. M.、Bergmann, E. M.、Bishop, P. N. 和 Bella, J. (2004) Proc. Natl. Acad. Sci. U.S.A. 101, 15633–15638）。核心蛋白聚糖是否以二聚体形式结合胶原蛋白一直存在争议。使用分析超速离心，我们确定了小鼠核心蛋白聚糖二聚体的解离常数为 1.37 ± 0.30 μm。通过将糖基化位点工程化到二聚体界面中可以消除二聚化；其他界面突变体仍然是二聚体。在热解折叠实验中，单体突变体与野生型核心蛋白聚糖一样稳定。无论突变蛋白是否保留二聚化能力，核心蛋白聚糖凹面的突变都会消除胶原蛋白的结合。我们得出的结论是，核心蛋白聚糖的凹面介导胶原蛋白结合，因此二聚体必须解离才能结合胶原蛋白。
Background: In the crystal structure of decorin, the concave faces of two monomers interact to form a tight dimer. Results: The decorin dimer in solution is in equilibrium with stable monomers, and mutations on the concave face abolish collagen binding. Conclusion: Decorin binds collagen as a monomer. Significance: These findings help resolve the controversy about the functional oligomeric state of decorin. Decorin, the prototypical small leucine-rich proteoglycan, binds to collagen and thereby regulates collagen assembly into fibrils. The crystal structure of the decorin core protein revealed a tight dimer formed by the association of two monomers via their concave faces (Scott, P. G., McEwan, P. A., Dodd, C. M., Bergmann, E. M., Bishop, P. N., and Bella, J. (2004) Proc. Natl. Acad. Sci. U.S.A. 101, 15633–15638). Whether decorin binds collagen as a dimer has been controversial. Using analytical ultracentrifugation, we determined a dissociation constant of 1.37 ± 0.30 μm for the mouse decorin dimer. Dimerization could be abolished by engineering glycosylation sites into the dimer interface; other interface mutants remained dimeric. The monomeric mutants were as stable as wild-type decorin in thermal unfolding experiments. Mutations on the concave face of decorin abolished collagen binding regardless of whether the mutant proteins retained the ability to dimerize or not. We conclude that the concave face of decorin mediates collagen binding and that the dimer therefore must dissociate to bind collagen.