Effective intermediate-spin iron in O₂-transporting heme proteins.

ABSTRACT: Proteins carrying an iron-porphyrin (heme) cofactor are essential for biological O₂ management. The nature of Fe-O₂ bonding in hemoproteins is debated for decades. We used energy-sampling and rapid-scan X-ray Kβ emission and K-edge absorption spectroscopy as well as quantum chemistry to determine molecular and electronic structures of unligated (deoxy), CO-inhibited (carboxy), and O₂-bound (oxy) hemes in myoglobin (MB) and hemoglobin (HB) solutions and in porphyrin compounds at 20-260 K. Similar metrical and spectral features revealed analogous heme sites in MB and HB and the absence of low-spin (LS) to high-spin (HS) conversion. Amplitudes of Kβ main-line emission spectra were directly related to the formal unpaired Fe(d) spin count, indicating HS Fe(II) i

SUBMITTER: Schuth N 

PROVIDER: S-EPMC5559043 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature