Get access

Functional role of a protein foldon—An Ω-loop foldon controls the alkaline transition in ferricytochrome c

Authors

  • Haripada Maity,

    Corresponding author
    1. The Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
    • The Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
    Search for more papers by this author
  • Jon N. Rumbley,

    1. The Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
    Current affiliation:
    1. Department of Chemistry, University of Minnesota, 313 Chemistry, 1039 University Dr., Duluth, MN 55812
    Search for more papers by this author
  • S. Walter Englander

    1. The Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
    Search for more papers by this author

Abstract

Hydrogen exchange results for cytochrome c and several other proteins show that they are composed of a number of foldon units which continually unfold and refold and account for some functional properties. Previous work showed that one Ω-loop foldon controls the rate of the structural switching and ligand exchange behavior of cytochrome c known as the alkaline transition. The present work tests the role of foldons in the alkaline transition equilibrium. We measured the effects of denaturant and 14 destabilizing mutations. The results show that the ligand exchange equilibrium is controlled by the stability of the same foldon unit implicated before. In addition, the results obtained confirm the ε-amino group of Lys79 and Lys73 as the alkaline replacement ligands and bear on the search for a triggering group. Proteins 2005. © 2005 Wiley-Liss, Inc.

Ancillary