Formation of Domain-Swapped Oligomer of Cytochrome c from Its Molten Globule State Oligomer

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• 作者：Megha Subhash Deshpande ; Partha Pratim Parui ; Hironari Kamikubo ; Masaru Yamanaka ; Satoshi Nagao ; Hirofumi Komori ; Mikio Kataoka ; Yoshiki Higuchi ; Shun Hirota
• 刊名：Biochemistry
• 出版年：2014
• 出版时间：July 22, 2014
• 年：2014
• 卷：53
• 期：28
• 页码：4696-4703
• 全文大小：409K
• ISSN：1520-4995

文摘

Many proteins, including cytochrome c (cyt c), have been shown to form domain-swapped oligomers, but the factors governing the oligomerization process remain unrevealed. We obtained oligomers of cyt c by refolding cyt c from its acid molten globule state to neutral pH state under high protein and ion concentrations. The amount of oligomeric cyt c obtained depended on the nature of the anion (chaotropic or kosmotropic) in the solution: ClO₄^{鈥?/sup> (oligomers, 11% 卤 2% (heme unit)), SCN鈥?/sup> (10% 卤 2%), I鈥?/sup> (6% 卤 2%), NO₃鈥?/sup> (3% 卤 1%), Br鈥?/sup> (2% 卤 1%), Cl鈥?/sup> (2% 卤 1%), and SO₄2鈥?/sup> (3% 卤 1%) for refolding of 2 mM cyt c (anion concentration 125 mM). Dimeric cyt c obtained by refolding from the molten globule state exhibited a domain-swapped structure, in which the C-terminal 伪-helices were exchanged between protomers. According to small-angle X-ray scattering measurements, approximately 25% of the cyt c molecules were dimerized in the molten globule state containing 125 mM ClO₄鈥?/sup>. These results indicate that a certain amount of molten globule state oligomers of cyt c convert to domain-swapped oligomers during refolding and that the intermolecular interactions necessary for domain swapping are present in the molten globule state.}