Co-rebinding in myoglobin as seen by time-resolved X-ray absorption spectroscopy

The dynamics of selected conformational coordinates, key roles in the under standing of the CO-rebinding process, are investigated in horse heart carbo nmonoxy myoglobin (MbCO) through time-resolved X-ray absorption spectroscop y. We present here the results obtained at 90 K in the second time scale. T he approach of the CO molecule towards the Fe atom in the active site pocke t is speculated to act as a natural precursor to the Fe displacement with t he consequent undoming of the protein porphyrin plane. The arrangement of t he Fe-C-O bonding angle geometry follows and the final MbCO active site con figuration is completely reached within 1 min.