Crystal structure of K72A variant of Human Cytochrome c

Experimental Data Snapshot

  • Resolution: 1.25 Å
  • R-Value Free: 0.166 
  • R-Value Work: 0.147 
  • R-Value Observed: 0.148 

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Effect of a K72A Mutation on the Structure, Stability, Dynamics, and Peroxidase Activity of Human Cytochrome c.

Nold, S.M.Lei, H.Mou, T.C.Bowler, B.E.

(2017) Biochemistry 56: 3358-3368

  • DOI: https://doi.org/10.1021/acs.biochem.7b00342
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    We test the hypothesis that Lys72 suppresses the intrinsic peroxidase activity of human cytochrome c, as observed previously for yeast iso-1-cytochrome c [McClelland, L. J., et al. (2014) Proc. Natl. Acad. Sci. U. S. A. 111, 6648-6653]. A 1.25 Å X-ray structure of K72A human cytochrome c shows that the mutation minimally affects structure. Guanidine hydrochloride denaturation demonstrates that the K72A mutation increases global stability by 0.5 kcal/mol. The K72A mutation also increases the apparent pK a of the alkaline transition, a measure of the stability of the heme crevice, by 0.5 unit. Consistent with the increase in the apparent pK a , the rate of formation of the dominant alkaline conformer decreases, and this conformer is no longer stabilized by proline isomerization. Peroxidase activity measurements show that the K72A mutation increases k cat by 1.6-4-fold at pH 7-10, an effect larger than that seen for the yeast protein. X-ray structures of wild type and K72A human cytochrome c indicate that direct interactions of Lys72 with the far side of Ω-loop D, which are seen in X-ray structures of horse and yeast cytochrome c and could suppress peroxidase activity, are lacking. Instead, we propose that the stronger effect of the K72A mutation on the peroxidase activity of human versus yeast cytochrome c results from relief of steric interactions between the side chains at positions 72 and 81 (Ile in human vs Ala in yeast), which suppress the dynamics of Ω-loop D necessary for the intrinsic peroxidase activity of cytochrome c.

  • Organizational Affiliation

    Division of Biological Sciences, University of Montana , Missoula, Montana 59812, United States.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cytochrome c
A, B
104Homo sapiensMutation(s): 0 
Gene Names: CYCSCYC
UniProt & NIH Common Fund Data Resources
Find proteins for P99999 (Homo sapiens)
Explore P99999 
Go to UniProtKB:  P99999
PHAROS:  P99999
GTEx:  ENSG00000172115 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP99999
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.25 Å
  • R-Value Free: 0.166 
  • R-Value Work: 0.147 
  • R-Value Observed: 0.148 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 56.794α = 90
b = 37.902β = 116.79
c = 60.254γ = 90
Software Package:
Software NamePurpose
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2017-09-06
    Type: Initial release
  • Version 1.1: 2023-10-04
    Changes: Data collection, Database references, Derived calculations, Refinement description