Abstract
Protein dynamics on the subnanosecond to microsecond time scale was investigated for the isolated heme domain of a gas sensor protein, EcDOS, with time-resolved ultraviolet resonance Raman (UVRR) spectroscopy. Rapid structural changes (<0.5 ns) due to CO dissociation and nanosecond structural relaxation following geminate recombination of CO were observed through a Raman band of Trp53 located near the heme. Microsecond transient UVRR spectra showed several phases of intensity changes in both Trp and Tyr bands. In hundreds of nanoseconds after CO photodissociation, the W18, W16, and W3 bands of Trp residues and Y8a band of Tyr residues decreased in intensity and were followed by the intensity recovery of Tyr band in 50 μs and of Trp bands in hundreds microseconds. This observation demonstrates that a change in the heme ligation triggers conformational changes in the protein moiety through heme side chains.
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