| Autor: |
Ioanitescu, Anda I., Van Doorslaer, Sabine, Dewilde, Sylvia, Endeward, Burkhard, Moens, Luc |
| Předmět: |
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| Zdroj: |
Molecular Physics; 8/10/2007, Vol. 105 Issue 15/16, p2073-2086, 14p, 1 Diagram, 3 Charts, 5 Graphs |
| Abstrakt: |
Cytoglobin is a vertebrate globin with an as yet unidentified function. In this work, S- and X-band pulsed EPR methods were used to elucidate the heme environment of ferric wild-type human cytoglobin (wt CYGB). The data resolve an earlier conflict between two X-ray diffraction studies, and show that the heme iron is bis-histidine ligated with both Fe-His bonds having comparable strength. Similar X-band EPR techniques were applied to study the heme-pocket environment of the ferric HE7Q mutant of CYGB (HE7Q CYGB). No distal water was found to coordinate to the heme iron, in contrast to the known metaquo form of the HE7Q mutant of myoglobin. The hyperfine and nuclear-quadrupole couplings of the directly coordinating heme and histidine nitrogens in ferric wt CYGB and HE7Q CYGB are derived and compared with known data on other ferric porphyrin compounds and heme proteins. Also, X-band CW EPR techniques were used in combination with absorption spectroscopy to investigate the ligation and oxidation state of wt CYGB in E. coli cells over-expressing this globin. Wt CYGB is found predominantly in the F8His-Fe2+-E7His form, whereby a small fraction of the protein exhibits the F8His-Fe2+-NO form. All present results are compared in detail with recent studies on neuroglobin, another member of the vertebrate globin family characterized by a bis-histidine coordination of the heme iron in both its ferrous and ferric forms. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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