Cleland J L, Randolph T W
Department of Chemical Engineering, Yale University, New Haven, Connecticut 06520.
J Biol Chem. 1992 Feb 15;267(5):3147-53.
Polyethylene glycol has been shown to bind to the molten globule intermediate on the bovine carbonic anhydrase B folding pathway. The mechanism of this interaction has been extensively probed. Polyethylene glycol (PEG) binds weakly to the molten globule first intermediate as measured by hydrophobic interaction chromatography, but PEG does not bind to either the native state or the second intermediate. The binding of PEG to the molten globule has been confirmed with both intrinsic fluorescence and fluorescence quenching experiments which indicate a single PEG-binding site on the molten globule. Electron paramagnetic resonance spectroscopic studies with nitroxide-labeled PEG also indicate a single binding site. Additional electron paramagnetic resonance studies with spin-labeled carbonic anhydrase B suggest that a conformational change occurs in the molten globule intermediate after PEG binds to the surface. The formation of a PEG-molten globule complex results in a reduction in self-association of this compact hydrophobic structure. PEG-molten globule complex formation is analogous to the observed interaction between chaperonins and a molten globule intermediate (Martin, J., Langer, T., Boteva, R., Schramel, A., Horwich, A.L., and Hartl, F.U. (1991) Nature 352, 36-42).
聚乙二醇已被证明可与牛碳酸酐酶B折叠途径中的熔融球状体中间体结合。这种相互作用的机制已被广泛探究。通过疏水相互作用色谱法测定，聚乙二醇（PEG）与熔融球状体的第一个中间体结合较弱，但PEG既不与天然状态结合，也不与第二个中间体结合。通过固有荧光和荧光猝灭实验证实了PEG与熔融球状体的结合，这表明熔融球状体上有一个单一的PEG结合位点。用氮氧化物标记的PEG进行的电子顺磁共振光谱研究也表明有一个单一的结合位点。用自旋标记的碳酸酐酶B进行的额外电子顺磁共振研究表明，PEG与表面结合后，熔融球状体中间体会发生构象变化。PEG - 熔融球状体复合物的形成导致这种紧密疏水结构的自缔合减少。PEG - 熔融球状体复合物的形成类似于伴侣蛋白与熔融球状体中间体之间观察到的相互作用（Martin, J., Langer, T., Boteva, R., Schramel, A., Horwich, A.L., and Hartl, F.U. (1991) Nature 352, 36 - 42）。
