Ultraviolet resonance Raman spectroscopy reveals that, when heated at pH 3, a substantial fraction (30%) of cytochrome c converts to a β-sheet structure, at the expense of turns and helices. β-sheet formation is rapid, exhibiting a 2 μs rise time, following a temperature jump. It is proposed that a short β-sheet segment, comprising residues 37-39 and 58-61, extends itself into the large 37-61 loop when the latter is destabilized by protonation of H26, which forms an anchoring H-bond to loop residue P44. This conformation change ruptures the Met80-Fe bond, as revealed by changes in ligation-sensitive heme-resonant Raman bands. It also induces peroxidase activity with the same temperature profile. This process is suggested to model the apoptotic peroxidation of cardiolipin by cytochrome c.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry