Open AccessThe structural basis of urea‐induced protein unfolding in β‐catenin
Author(s) -
Wang Chao,
Chen Zhongzhou,
Hong Xia,
Ning Fangkun,
Liu Haolin,
Zang Jianye,
Yan Xiaoxue,
Kemp Jennifer,
Musselman Catherine A.,
Kutateladze Tatinna G.,
Zhao Rui,
Jiang Chengyu,
Zhang Gongyi
Publication year - 2014
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s1399004714018094
Subject(s) - guanidine , urea , hydrogen bond , chemistry , hydrochloride , polyethylene glycol , denaturation (fissile materials) , crystallography , hydrophobic effect , circular dichroism , molecule , biophysics , biochemistry , organic chemistry , nuclear chemistry , biology
Although urea and guanidine hydrochloride are commonly used to denature proteins, the molecular underpinnings of this process have remained unclear for a century. To address this question, crystal structures of β‐catenin were determined at various urea concentrations. These structures contained at least 105 unique positions that were occupied by urea molecules, each of which interacted with the protein primarily via hydrogen bonds. Hydrogen‐bond competition experiments showed that the denaturing effects of urea were neutralized when polyethylene glycol was added to the solution. These data suggest that urea primarily causes proteins to unfold by competing and disrupting hydrogen bonds in proteins. Moreover, circular‐dichroism spectra and nuclear magnetic resonance (NMR) analysis revealed that a similar mechanism caused protein denaturation in the absence of urea at pH levels greater than 12. Taken together, the results led to the conclusion that the disruption of hydrogen bonds is a general mechanism of unfolding induced by urea, high pH and potentially other denaturing agents such as guanidine hydrochloride. Traditionally, the disruption of hydrophobic interactions instead of hydrogen bonds has been thought to be the most important cause of protein denaturation.