Heme-protein vibrational couplings in cytochrome c provide a dynamic link that connects the heme-iron and the protein surface

摘要: The active site of cytochrome c (Cyt c) consists a heme covalently linked to pentapeptide segment (Cys-X-X-Cys-His), which provides link between the and protein surface, where redox partners Cyt bind. To elucidate vibrational properties c, nuclear resonance spectroscopy (NRVS) measurements were performed on 57Fe-labeled ferric Hydrogenobacter thermophilus c552, including 13C8-heme–, 13C515N-Met–, 13C15N-polypeptide (pp)–labeled samples, revealing heme-based modes in 200- 450-cm−1 spectral region. Simulations NRVS spectra H. c552 allowed for complete assignment Fe spectrum protein-bound heme, as well quantitative determination amount mixing local vibrations pp from Cys-X-X-Cys-His motif. These results provide basis propose that heme-pp dynamic couplings play role electron transfer (ET) by coupling directly at protein–protein interface. This could allow direct transduction thermal (vibrational) energy surface is released protein/protein complex formation, or it modulate minimize reorganization energy. Both mechanisms lower barriers ET. Notably, conformation distal Met side chain fine-tuned localize mixed within 250- 400-cm−1 findings point particular orientation maximizes