Blue Myoglobin Reconstituted with an Iron Porphycene Shows Extremely High Oxygen Affinity

Myoglobin will be a good scaffold for engineering a function into proteins. To modulate the physiological function of myoglobin, almost all approaches have been demonstrated by site-directed mutagenesis, however, there are few studies which show a significant improvement in the function. In contrast...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2002-09, Vol.124 (38), p.11226-11227
Main Authors: Hayashi, Takashi, Dejima, Hirohisa, Matsuo, Takashi, Sato, Hideaki, Murata, Dai, Hisaeda, Yoshio
Format: Article
Language:English
Subjects:
Analytical, structural and metabolic biochemistry
Biological and medical sciences
Fundamental and applied biological sciences. Psychology
Heme - chemistry
Kinetics
Metalloproteins
Myoglobin - chemistry
Myoglobin - metabolism
Other metalloproteins
Oxidation-Reduction
Oxygen - chemistry
Oxygen - metabolism
Porphyrins - chemistry
Proteins
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Summary:Myoglobin will be a good scaffold for engineering a function into proteins. To modulate the physiological function of myoglobin, almost all approaches have been demonstrated by site-directed mutagenesis, however, there are few studies which show a significant improvement in the function. In contrast, we focused on the replacement of heme in the protein with an artificial prosthetic group. Recently, we prepared a novel myoglobin reconstituted with an iron porphycene as a structural isomer of mesoheme. The bluish colored reconstituted myoglobin is relatively stable and the deoxymyoglobin reversibly binds ligands. Interestingly, the O2 affinity of the reconstituted myoglobin, 1.1 × 109 M-1, is a significant 1,400-fold higher than that of the native myoglobin. Furthermore, the unfavorable autoxidation kinetics show 7-fold decrease in rate for the reconstituted myoglobin relative to the native myoglobin, indicating the stable oxy-form against autoxidation. The net results come from the slow dissociation of the O2 ligand in the reconstituted myoglobin, k off = 0.11 s-1, because of the formation of strong hydrogen bond between His64 and negatively charged dioxygen. The present study indicates that the replacement of native heme with an artificially created prosthetic group will give us a unique function into a hemoprotein.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja0265052