Formation of a hydrophobic cluster in denatured bovine pancreatic trypsin inhibitor.
Formation of a hydrophobic cluster in denatured bovine pancreatic trypsin inhibitor.
复制标题
变性牛胰腺胰蛋白酶抑制剂中疏水簇的形成。
DOI：
10.1006/jmbi.1994.1153
复制
发表时间：
1994
影响因子：
5.6
通讯作者：
Kim,PS
中科院分区：
文献类型：
--
作者：
Lumb,KJ;Kim,PS
牛胰胰蛋白酶抑制剂（BPTI）在其三个二硫键还原时解折叠。BPTI还原态的重组模型[R]Ala，其中6个Cys残基全部被Ala取代，已在大肠杆菌中表达。1H核磁共振谱表明[R]Aladoes不含稳定的二级结构。然而，存在一些化学位移分散，这表明[R]Ala中存在非随机相互作用。特别地，Ile19的侧链质子共振Ile18的那些的高场。使用八残基肽模型P17·24（对应于BPTI的残基17至24）研究了这一观察结果。在[R] Ala中观察到的Ile残基的非随机化学位移分散也发生在P17·24中，表明P17·24含有类似于[R]Ala相应区域中发现的相互作用。在P17·24中观察到的唯一残基间核Overhauser效应发生在Tyr 21的环质子和Ile 19的γ CH 3基团之间，表明这些质子非常接近。P17·24中Tyr 21被Ala取代导致Ile共振的化学位移色散的损失，这表明Ile 19共振的高场位移是由于Tyr 21邻近引起的环电流位移。总的来说，这些结果表明Ile 19的侧链至少在某些时候位于Tyr 21的芳环平面上方。这两个残基参与了P17·24的疏水簇和BPTI的变性状态。
Bovine pancreatic trypsin inhibitor (BPTI) unfolds upon reduction of its three disulfide bonds. A recombinant model of the reduced state of BPTI, called [R]Ala, in which all six Cys residues are replaced with Ala, has been expressed inEscherichia coli.1H nuclear magnetic resonance spectroscopy shows that [R]Aladoes not contain stable secondary structure. Some chemical shift dispersion exists, however, suggesting the existence of non-random interactions in [R]Ala. In particular, the side-chain protons of Ile19 resonate upfield of those of Ile18. This observation was investigated using an eight residue peptide model, P17·24, corresponding to residues 17 to 24 of BPTI. The non-random chemical shift dispersion of the Ile residue observed in [R]Alaalso occurs in P17·24, indicating that P17·24contains interactions that are similar to those found in the corresponding region of [R]Ala. The only interresidue nuclear Overhauser effects observed in P17·24are between the ring protons of Tyr21 and the γCH3group of Ile19, indicating that these protons are in close proximity. Substitution of Tyr21 by Ala in P17·24results in the loss of the chemical shift dispersion of the Ile resonances, suggesting that the upfield shifts of the Ile19 resonances are due to ring current shifts arising from the proximity of Tyr21. Collectively, these results suggest that the side-chain of Ile19 is positioned at least some of the time above the plane of the aromatic ring of Tyr21. We conclude that these two residues participate in a hydrophobic cluster in P17·24and in the denatured state of BPTI.