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Figure 4.
FIG. 4. Reorganization of the hydrogen bond network at the
heme distal site near the dimer interface. a, comparison of heme
distal sites between Fe^3+ (cyan) and Fe^2+ (yellow) forms of Ec
DOSH. Residues 31-85 and 97-132 of subunit I in each form were
superimposed. Residues in subunit II are colored in blue for the
Fe^3+ form and orange for the Fe^2+ form. Hydrogen bonds are
presented as dotted lines. Met-95 coordination to the heme iron
upon reduction induces reorganization of the hydrogen bond
network at the heme distal site. Side chains of Phe-113 and
Leu-115 move slightly to adjust to heme-ligand switching. These
changes induce hydrogen bond formation between Phe-113 and
Arg-131. No effects were observed on the hydrogen bond between
Ser-116 and Met-30. The buried dimer surface areas of the Fe^3+
form (b) and Fe^2+ form (c) of subunit I are shown. Distances
between the surfaces of each subunit were calculated with MOLMOL
and ranged from <2 Å (red) to >7 Å (blue). Met-30
and Arg-131 of subunit II are presented as a stick model.
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