2024-03-28T17:25:23Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/729372022-11-17T02:08:08Zhdl_2115_20039hdl_2115_116Polyethylene glycol promotes autoxidation of cytochrome cSato, WataruUchida, TakeshiSaio, TomohideIshimori, KoichiroHemeCytochrome cElectron transferDehydration464Cytochrome c (Cyt c) was rapidly oxidized by molecular oxygen in the presence, but not absence of PEG. The redox potential of heme c was determined by the potentiometric titration to be +236 ± 3 mV in the absence of PEG, which was negatively shifted to +200 ± 4 mV in the presence of PEG. The underlying the rapid oxidation was explored by examining the structural changes in Cyt c in the presence of PEG using UV–visible absorption, circular dichroism, resonance Raman, and fluorescence spectroscopies. These spectroscopic analyses suggested that heme oxidation was induced by a modest tertiary structural change accompanied by a slight shift in the heme position (<1.0 Å) rather than by partial denaturation, as is observed in the presence of cardiolipin. The near-infrared spectra showed that PEG induced dehydration from Cyt c, which triggered heme displacement. The primary dehydration site was estimated to be around surface-exposed hydrophobic residues near the heme center: Ile81 and Val83. These findings and our previous studies, which showed that hydrated water molecules around Ile81 and Val83 are expelled when Cyt c forms a complex with CcO, proposed that dehydration of these residues is functionally significant to electron transfer from Cyt c to CcO.ElsevierJournal Articleapplication/pdfhttp://hdl.handle.net/2115/72937https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/72937/1/j.bbagen.2018.03.010-HUSCAP.pdf0304-4165Biochimica et Biophysica Acta (BBA) - General Subjects18626133913492018-06enginfo:doi/10.1016/j.bbagen.2018.03.010© 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/author