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Proton nuclear magnetic resonance study of the ferrous derivatives of the dimeric and tetrameric hemoglobin from the mollusc Scapharca inaequivalvis
Author(s) -
Inubushi Toshiro,
Yonetani Takashi,
Chiancone Emilia
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)81239-0
Subject(s) - tetramer , chemistry , crystallography , histidine , hydrogen bond , hemoglobin , hemeprotein , proton , imidazole , heme , proton nmr , resonance (particle physics) , protein subunit , heterotetramer , nuclear magnetic resonance , stereochemistry , molecule , biochemistry , physics , organic chemistry , amino acid , particle physics , quantum mechanics , gene , enzyme
Proton NMR spectra have been measured for the two hemoglobins from the mollusc Scapharca inaequivalvis: HbI, a homodimer, and HbII, a heterotetramer. These hemoglobins are endowed with a unique subunit assembly, since the heme carrying E and F helices are involved in the major intersubunit contact. In the far‐downfield region of hyperfine‐shifted resonances the spectra of HbI and HbII in the deoxy state show respectively one (66.7 ppm) and two (67.8 and 63.6 ppm) exchangeable signals of the proximal histidine NδH groups, the resonance position being indicative of a significant strain in the iron‐imidazole interaction. In the hydrogen‐bonded proton region, inter‐ and intrasubunit hydrogen‐bonded proton signals have been detected for both hemoglobins. Deoxy‐HbI shows two unique downfield resonances at 11.83 and 11.51 ppm which disappear in the oxygenated state, suggesting that the corresponding hydrogen bonds are involved in the stabilization of the tertiary and/or quaternary structure of the deoxy form. HbII shows even smaller changes in this region upon changes in ligation state. These results therefore provide further proof that, at variance with the vertebrate hemoglobin tetramer, the unique subunit assembly of these proteins is stabilized mainly by hydrophobic interactions.