The response of Ω-loop D dynamics to truncation of trimethyllysine 72 of yeast iso-1-cytochrome c depends on the nature of loop deformation

Levi J. McClelland, Sean M. Seagraves, Md Khurshid Alam Khan, Melisa M. Cherney, Swati Bandi, Justin E. Culbertson, Bruce E. Bowler

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Abstract Trimethyllysine 72 (tmK72) has been suggested to play a role in sterically constraining the heme crevice dynamics of yeast iso-1-cytochrome c mediated by the Ω-loop D cooperative substructure (residues 70-85). A tmK72A mutation causes a gain in peroxidase activity, a function of cytochrome c that is important early in apoptosis. More than one higher energy state is accessible for the Ω-loop D substructure via tier 0 dynamics. Two of these are alkaline conformers mediated by Lys73 and Lys79. In the current work, the effect of the tmK72A mutation on the thermodynamic and kinetic properties of wild-type iso-1-cytochrome c (yWT versus WT∗) and on variants carrying a K73H mutation (yWT/K73H versus WT∗/K73H) is studied. Whereas the tmK72A mutation confers increased peroxidase activity in wild-type yeast iso-1-cytochrome c and increased dynamics for formation of a previously studied His79-heme alkaline conformer, the tmK72A mutation speeds return of the His73-heme alkaline conformer to the native state through destabilization of the His73-heme alkaline conformer relative to the native conformer. These opposing behaviors demonstrate that the response of the dynamics of a protein substructure to mutation depends on the nature of the perturbation to the substructure. For a protein substructure which mediates more than one function of a protein through multiple non-native structures, a mutation could change the partitioning between these functions. The current results suggest that the tier 0 dynamics of Ω-loop D that mediates peroxidase activity has similarities to the tier 0 dynamics required to form the His79-heme alkaline conformer.

Original languageEnglish
Article number1267
Pages (from-to)805-819
Number of pages15
JournalJournal of Biological Inorganic Chemistry
Issue number5
StatePublished - Jul 27 2015


  • Alkaline conformational transition
  • Apoptosis
  • Conformationally gated electron transfer
  • Cooperative substructure dynamics
  • Cytochrome c


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