Cairoli S, Iametti S, Bonomi F
Dipartimento di Scienze Molecolari Agroalimentari, Università di Milano, Italy.
J Protein Chem. 1994 Apr;13(3):347-54. doi: 10.1007/BF01901568.
Modifications in the exposure to the solvent of hydrophobic residues, changes in their organization into surface hydrophobic patches, and alterations in the dimerization equilibrium of beta-lactoglobulin upon thermal treatment at neutral pH were studied. Exposure of tryptophan residues was temperature dependent and was essentially completed on the time scale of seconds. Reorganization of generic hydrophobic protein patches on the protein surface was monitored through binding of 1,8-anilinonaphthalenesulfonate, and was much slower than changes in tryptophan exposure. Different phases in surface hydrophobicity changes were related to the swelling and the subsequent collapse of the protein, which formed a metastable swollen intermediate. Heat treatment of beta-lactoglobulin also resulted in the formation of soluble oligomeric aggregates. The aggregation process was studied as a function of temperature, demonstrating that (i) dimer dissociation was a necessary step in a sequential polymerization mechanism and (ii) cohesion of hydrophobic patches was the major driving force for aggregation.
研究了在中性pH值下热处理时，β-乳球蛋白疏水性残基与溶剂接触的变化、它们组织成表面疏水斑块的变化以及二聚化平衡的改变。色氨酸残基的暴露与温度有关，且在数秒的时间尺度上基本完成。通过1,8-苯胺基萘磺酸盐的结合监测蛋白质表面一般疏水蛋白斑块的重组，其速度比色氨酸暴露的变化慢得多。表面疏水性变化的不同阶段与蛋白质的膨胀和随后的塌陷有关，蛋白质形成了一个亚稳态的膨胀中间体。β-乳球蛋白的热处理还导致形成可溶性寡聚聚集体。研究了聚集过程与温度的关系，表明：(i) 二聚体解离是连续聚合机制中的一个必要步骤；(ii) 疏水斑块的凝聚是聚集的主要驱动力。
