title: Contributions of the C-terminal helix to the structural stability of a hyperthermophilic Fe-superoxide dismutase (TcSOD).
abstract: 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 GdnHCl-induced 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.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Sha
authors.initials: S
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Yong-Bin
authors.initials: YB
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Zhi-Yang
authors.initials: ZY
authors.lastname: Dong
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D017353:Gene Deletion; D019791:Guanidine / Q000737:chemistry; D006358:Hot Temperature; D007501:Iron / Q000737:chemistry; D008969:Molecular Sequence Data; D017354:Point Mutation; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D007501:Iron; D013482:Superoxide Dismutase; D019791:Guanidine