Structure and assembly of the heterotrimeric and homotrimeric C-propeptides of type I collagen : Significance of the α2(I) chain
Structure and assembly of the heterotrimeric and homotrimeric C-propeptides of type I collagen : Significance of the α2(I) chain
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I 型胶原异源三聚体和同源三聚体 C 前肽的结构和组装：α2(I) 链的意义
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
A. Veis
中科院分区：
文献类型：
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作者：
J. Malone;K. Alvares;A. Veis
I型前胶原分子的组装始于C-pro α 1（I）和C-pro α 2（I）结构域之间的相互作用。C-前肽结构域本身具有不同结构的亚结构域。重要的问题是链缔合从何处开始以及导致[C-pro α 1（I）]2[C-pro α 2（I）]异源三聚体优先形成的链选择性的基础。这些问题是通过能量最小化建模的个人C-前肽结构，他们的对接相互作用的研究，并比较异源三聚体和同源三聚体的C-前体的结构和稳定性。比较显示C-pro α 2链对组装的三聚体C-前肽的结构的显著影响。在建模中，这三条链被锚定并通过短的C-末端胶原三螺旋片段配准，随后是处于其对接构象的C-端肽，然后允许剩余的C-前肽链相互作用并对接。令人惊讶的是，前肽三聚化没有通过先前提出的C-前肽的N-末端“寡聚化结构域”进行[McAlinden等人（2003）J.Biol.Chem.278，42200]，而是在I型前胶原链的最C-末端结构域中进行。分子动力学显示异源三聚体组装开始，在球状G2 α 2和G2 α 1（2）结构域之间形成二聚体，然后在G1结构域处三聚化。在假定的寡聚卷曲螺旋结构域中的组装起始是不可能的，因为在α 2 C-前肽链的N-末端的位置3、7和11处存在Pro残基。为了证实计算结果和提出的组装途径，G2 α 1和G2 α 2结构域重组制备麦芽糖结合蛋白构建体，并通过动态光散射和凝胶过滤色谱法研究它们的相互作用。在检测的条件下，MBP保持为单体，MBP-G2 α 1和MBP-G2 α 2单独形成二聚体，但MBP-G2 α 1和MBP-G2 α 2的2：1混合物有利于三聚体形成。因此，I型胶原蛋白C-前肽的C-末端球状结构域（G2）在分子间组装和异源三聚体选择性的起始中起着至关重要的作用。
Assembly of the type I procollagen molecule begins with interactions among the C-pro alpha1(I) and C-pro alpha2(I) domains. The C-propeptide domains themselves have subdomains of distinct structures. The important questions are where chain association begins and the basis of the chain selectivity which leads to the preferential formation of the [C-pro alpha1(I)]2[C-pro alpha2(I)] heterotrimer. These questions are addressed by energy minimization modeling of the individual C-propeptide structures, study of their docking interactions, and comparison of the heterotrimeric and homotrimeric C-pro structures and stability. The comparisons show the remarkable impact of the C-pro alpha2 chain on the structure of the assembled trimeric C-propeptide. In the modeling, the three chains were anchored and registered by a short C-terminal collagen triple-helical segment followed by the C-telopeptides in their docked conformation, and then the remaining C-propeptide chains were allowed to interact and dock. Surprisingly, propeptide trimerization did not proceed through the previously proposed N-terminal "oligomerization domain" of the C-propeptide [McAlinden et al. (2003) J. Biol. Chem. 278, 42200] but rather in the most C-terminal domains of type I procollagen chains. Molecular dynamics showed heterotrimer assembly to begin with dimer formation between globular G2alpha2 and the G2alpha1(2) domains followed by trimerization at the G1 domains. Assembly initiation in the putative oligomerization coiled-coil domain is not possible because of the Pro residues at positions 3, 7, and 11 at the N-terminus of the alpha2 C-propeptide chain. To confirm the computations and proposed assembly pathway, the G2alpha1 and G2alpha2 domains were prepared recombinantly as the maltose binding protein constructs, and their interactions were studied by dynamic light scattering and gel filtration chromatography. Under the conditions examined MBP remained as monomer, MBP-G2alpha1 and MBP-G2alpha2 alone formed dimers, but a 2:1 mixture of MBP-G2alpha1 and MBP-G2alpha2 favored trimer formation. Thus, the C-terminal globular domains (G2) of the type I collagen C-propeptides play a crucial role in the initiation of intermolecular assembly and heterotrimer selectivity.