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Open AccessArticle

Contributions of the C-Terminal Helix to the Structural Stability of a Hyperthermophilic Fe-Superoxide Dismutase (TcSOD)

by Sha Wang 1, Yong-Bin Yan 2,* and Zhi-Yang Dong 1,*
1
State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
2
State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China
*
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2009, 10(12), 5498-5512; https://doi.org/10.3390/ijms10125498
Received: 18 November 2009 / Revised: 16 December 2009 / Accepted: 17 December 2009 / Published: 23 December 2009
(This article belongs to the Section Biochemistry)
Hyperthermophilic superoxide dismutases (SODs) are of particular interest due to their potential industrial importance and scientific merit in studying the molecular mechanisms of protein folding and stability. Compared to the mesophilic SODs, the hyperthermostable Fe-SODs (TcSOD and ApSOD) have an extended C-terminal helix, which forms an additional ion-pairing network. In this research, the role of the extended C-terminus in the structural stability of TcSOD was studied by investigating the properties of two deletion mutants. The results indicated that the ion-pairing network at the C-terminus had limited contributions to the stability of TcSOD against heat- and GdnHClinduced inactivation. The intactness of the C-terminal helix had dissimilar impact on the two stages of TcSOD unfolding induced by guanidinium chloride. The mutations slightly decreased the Gibbs free energy of the dissociation of the tetrameric enzymes, while greatly affected the stability of the molten globule-like intermediate. These results suggested that the additional ion-pairing network mainly enhanced the structural stability of TcSOD by stabilizing the monomers. View Full-Text
Keywords: Fe-superoxide dismutase; hyperthermophilic enzyme; thermostability; ion-pairing network; protein unfolding Fe-superoxide dismutase; hyperthermophilic enzyme; thermostability; ion-pairing network; protein unfolding
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Wang, S.; Yan, Y.-B.; Dong, Z.-Y. Contributions of the C-Terminal Helix to the Structural Stability of a Hyperthermophilic Fe-Superoxide Dismutase (TcSOD). Int. J. Mol. Sci. 2009, 10, 5498-5512.

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