Secondary Structures Associated With Alkaline Transition of Horse Heart Ferricytochrome C: An FTIR Study

Abstract

The spectra of amide I region (1700-1600cm-1) of horse heart ferricytochrome c at 20oC are reported at low ionic strength at of pH values between 7.0 and 11.5 encompassing the alkaline transition. The mid-infrared spectra can probe the protein secondary structures. The Fourier transform infrared spectroscopic technique is used to investigate the changes in the conformationally sensitive amide I band of cytochrome c with pH and ionic strength. Analysis of these results supports the hypothesis that an increase in the non-repetitive secondary structure during alkaline transition is at the expense of regular secondary structures. These strongly suggest that structural switching and ligand exchange behaviour of ferricytochrome c is accompanied by conformational change in the protein backbone.