Conformational toggling of yeast iso-1-cytochrome C in the oxidized and reduced states

• Published in: PloS one 2011-11, Vol.6 (11), p.e27219
• Main Authors: Lan, Wenxian, Wang, Zhonghua, Yang, Zhongzheng, Zhu, Jing, Ying, Tianlei, Jiang, Xianwang, Zhang, Xu, Wu, Houming, Liu, Maili, Tan, Xiangshi, Cao, Chunyang, Huang, Zhong-Xian
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Apoptosis; Aqueous solutions; Binding Sites; Biochemistry; Biology; Circular dichroism; Cytochrome; Cytochrome c; Cytochromes c1 - chemistry; Cytochromes c1 - genetics; Cytochromes c1 - physiology; Dichroism; Electron transfer; Electron Transport; Fungal Proteins - chemistry; Heme; Histidine; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Iron; Laboratories; Ligands; Mathematics; Molecular physics; Mutation; Natural products; Organic chemistry; Oxidation; Oxidation-Reduction; Peroxidase; Physics; Polypeptides; Prostheses; Protein Conformation; Protein structure; Proteins; Raman spectroscopy; Riveting; Spectroscopy; Spectrum Analysis; Structural analysis; Studies; Tertiary structure; Valence; Yeast
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0027219

To convert cyt c into a peroxidase-like metalloenzyme, the P71H mutant was designed to introduce a distal histidine. Unexpectedly, its peroxidase activity was found even lower than that of the native, and that the axial ligation of heme iron was changed to His71/His18 in the oxidized state, while to Met80/His18 in the reduced state, characterized by UV-visible, circular dichroism, and resonance Raman spectroscopy. To further probe the functional importance of Pro71 in oxidation state dependent conformational changes occurred in cyt c, the solution structures of P71H mutant in both oxidation states were determined. The structures indicate that the half molecule of cyt c (aa 50-102) presents a kind of "zigzag riveting ruler" structure, residues at certain positions of this region such as Pro71, Lys73 can move a big distance by altering the tertiary structure while maintaining the secondary structures. This finding provides a molecular insight into conformational toggling in different oxidation states of cyt c that is principle significance to its biological functions in electron transfer and apoptosis. Structural analysis also reveals that Pro71 functions as a key hydrophobic patch in the folding of the polypeptide of the region (aa 50-102), to prevent heme pocket from the solvent.