Figure 3.

Product of NO reaction by Fe_BMb is N₂O. Time dependent GC/MS measurements of N₂O formation by Fe(II)-Fe_BMb (A). Control reactions of NO with Fe²⁺ only (B) and wtMb (C). NO (~17 eq) was reacted with Fe(II)-Fe_BMb (0.6 mM protein, 1.5 mM or 2.5 eq Fe²⁺), Fe²⁺ (1.5 mM, no protein), or with wtMb (1 mM) and Fe²⁺ (2 mM or 2 eq). At 6 hr, 2 eq dithionite (1.2 mM) was added and allowed to react to simulate a second turnover. NO₂ (MW 46) was not detected. GC peaks have been normalized. N₂O yield (30%) was determined from a comparison of the ratio of the NO:N₂O peaks of the 30 MW:44 MW single ion chromatograms 2 hr after dithionite addition (after which additional N₂O formation was not observed), to that of known dithionite concentrations (2 hr after addition). Background N₂O formation (i.e., Fe²⁺ without protein) was subtracted from that of Fe(II)-Fe_BMb to estimate the yield.