Solution structure of the α-subunit of human chorionic gonadotropin
Solution structure of the α-subunit of human chorionic gonadotropin
复制标题
DOI：
10.1046/j.1432-1327.1999.00188.x
复制
发表时间：
1999-03-01
期刊：
影响因子：
--
通讯作者：
Vliegenthart, JFG
中科院分区：
文献类型：
--
作者：
Erbel, PJA;Karimi-Nejad, Y;Vliegenthart, JFG
使用自然丰度的 2D 同核和 2D 异核 H-1,C-13 NMR 光谱结合程序包 XPLOR 测定用内切 β-N-乙酰氨基葡萄糖苷酶-B (dg-alpha hCG) 去糖基化的 α,β 异二聚人绒毛膜促性腺激素 (hCG) 中 a 亚基的三维溶液结构。距离几何/模拟退火方案修改为允许对 α hCG 中存在的胱氨酸结基序进行有效建模。蛋白质结构用 620 个质子间距离限制进行建模，连接到 Asn78 的 GlcNAc 残基用 30 个蛋白质-碳水化合物和 3 个残基内 NOE 进行建模。 dg-alpha hCG 的解决方案结构由 27 个结构组成的整体表示。与二聚体的晶体结构相比，游离 dg-α hCG 的溶液结构表现出： (a) 结构无序增加（残基 33-57）； (b) Va176 和 Glu77 附近的不同主链构象； (c) 更大的灵活性。这些差异是由于缺乏与 β 亚基的相互作用造成的。因此，在dg-α hCG中，与完整二聚体相比，两个发夹环20-23和70-74彼此排列不同。 β-GlcNAc(78) 与β-发夹之间的疏水蛋白核心紧密相关。该结论基于从轴向 H1、H3、H5 原子和 β-GLcNAc(78) 的 N-乙酰质子到蛋白质核心的 NOE。 β-发夹之间的疏水性蛋白质玉米因此与溶剂隔离。
The three-dimensional solution structure of the a-subunit in the alpha,beta heterodimeric human chorionic gonadotropin (hCG), deglycosylated with endo-beta-N-acetylglucosaminidase-B (dg-alpha hCG), was determined using 2D homonuclear and 2D heteronuclear H-1,C-13 NMR spectroscopy at natural abundance in conjunction with the program package XPLOR The distance geometry/simulated annealing protocol was modified to allow for the efficient modelling of the cystine knot motif present in alpha hCG. The protein structure was modelled with 620 interproton distance restraints and the GlcNAc residue linked to Asn78 was modelled with 30 protein-carbohydrate and 3 intraresidual NOEs. The solution structure of dg-alpha hCG is represented by an ensemble of 27 structures. In comparison to the crystal structure of the dimer, the solution structure of free dg-alpha hCG exhibits: (a) an increased structural disorder (residues 33-57); (b) a different backbone conformation near Va176 and Glu77; and (c) a larger flexibility. These differences are caused by the absence of the interactions with the beta-subunit. Consequently, in foe dg-alpha hCG, compared to the intact dimer, the two hairpin loops 20-23 and 70-74 are arranged differently with respect to each other. The beta-GlcNAc(78) is tightly associated with the hydrophobic protein-core in between the beta-hairpins. This conclusion is based on the NOEs from the axial H1, H3, H5 atoms and the N-acetyl protons of beta-GLcNAc(78) to the protein-core. The hydrophobic protein-corn between the beta-hairpins is thereby shielded from the solvent.