Solution structure of the ubiquitin-associated domain of human BMSC-UbP and its complex with ubiquitin
Solution structure of the ubiquitin-associated domain of human BMSC-UbP and its complex with ubiquitin
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DOI：
10.1110/ps.051995006
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发表时间：
2006-06-01
期刊：
影响因子：
8
通讯作者：
Hu, Hong-Yu
中科院分区：
文献类型：
--
作者：
Chang, Yong-Gang;Song, Ai-Xin;Hu, Hong-Yu
泛素是一种重要的细胞信号，它针对蛋白质进行降解或调节其功能。先前发现的来源于骨髓基质细胞的BMSC-UBP蛋白在C端含有一个泛素相关(UBA)结构域，该结构域参与连接细胞过程和泛素系统。在这里，我们报道了人BMSC-UBP蛋白的UBA结构域及其与泛素的络合物的溶液核磁共振结构。结果表明，BMSC-UBP UBA结构域主要由三个α-螺旋组成，疏水斑块由螺旋-1、环-1和螺旋-3的C末端残基定义。M-G-I基序与大多数UBA结构域中保守的M/L-G-F/Y基序相似。化学位移微扰研究表明，UBA结构域通过疏水作用与保守的五链泛素β-折叠结合，其解离常数(Kd)约为17mM。通过化学位移映射结合HADDOK程序构建了BMSC-UBP UBA结构域与泛素的络合结构模型，与诱变研究结果一致。在复杂结构中，BMSC-UBP UBA的三个残基(Met76、Ile78和Leu99)形成三叉戟，将结构域锚定在由Leu8、Ile44、His68和Val70残基定义的泛素的疏水凹面上。这种复杂的结构可能为BMSC-UBP的功能提供线索，并为了解其他与BMSC-UBP UBA结构域有很高序列同源性的泛素相关蛋白的UBA结构域提供线索。
Ubiquitin is an important cellular signal that targets proteins for degradation or regulates their functions. The previously identified BMSC-UbP protein derived from bone marrow stromal cells contains a ubiquitin-associated(UBA) domain at the C terminus that has been implicated in linking cellular processes and the ubiquitin system. Here, we report the solution NMR structure of the UBA domain of human BMSC-UbP protein and its complex with ubiquitin. The structure determination was facilitated by using a solubility-enhancement tag ( SET) GB1, immunoglobulin G binding domain 1 of Streptococcal protein G. The results show that BMSC-UbP UBA domain is primarily comprised of three alpha-helices with a hydrophobic patch defined by residues within the C terminus of helix-1, loop-1, and helix-3. The M-G-I motif is similar to the M/L-G-F/Y motifs conserved in most UBA domains. Chemical shift perturbation study revealed that the UBA domain binds with the conserved five-stranded beta-sheet of ubiquitin via hydrophobic interactions with the dissociation constant (KD) of similar to 17 mu M. The structural model of BMSC-UbP UBA domain complexed with ubiquitin was constructed by chemical shift mapping combined with the program HADDOCK, which is in agreement with the result from mutagenesis studies. In the complex structure, three residues (Met76, Ile78, and Leu99) of BMSC-UbP UBA form a trident anchoring the domain to the hydrophobic concave surface of ubiquitin defined by residues Leu8, Ile44, His68, and Val70. This complex structure may provide clues for BMSC-UbP functions and structural insights into the UBA domains of other ubiquitin-associated proteins that share high sequence homology with BMSC-UbP UBA domain.