TY - JOUR
T1 - Crystal structures of the methane monooxygenase hydroxylase from Methylococcus capsulatus (Bath)
T2 - Implications for substrate gating and component interactions
AU - Rosenzweig, Amy C.
AU - Brandstetter, Hans
AU - Whittington, Douglas A.
AU - Nordlund, Pär
AU - Lippard, Stephen J.
AU - Frederick, Christin A.
PY - 1997
Y1 - 1997
N2 - The crystal structure of the nonheme iron-containing hydroxylase component of methane monooxygenase hydroxylase (MMOH) from Methylococcus capsulatus (Bath) has been solved in two crystal forms, one of which was refined to 1.7 Å resolution. The enzyme is composed of two copies each of three subunits (α2β2γ2), and all three subunits are almost completely α-helical, with the exception of two β hairpin structures in the (α subunit. The active site of each (α subunit contains one dinuclear iron center, housed in a four-helix bundle. The two iron atoms are octahedrally coordinated by 2 histidine and 4 glutamic acid residues as well as by a bridging hydroxide ion, a terminal water molecule, and at 4°C, a bridging acetate ion, which is replaced at -160°C with a bridging water molecule. Comparison of the results for two crystal forms demonstrates overall conservation and relative orientation of the domain structures. The most prominent structural difference identified between the two crystal forms is in an altered side chain conformation for Leu 110 at the active site cavity. We suggest that this residue serves as one component of a hydrophobic gate controlling access of substrates to and products from the active site. The leucine gate may be responsible for the effect of the B protein component on the reactivity of the reduced hydroxylase with dioxygen. A potential reductase binding site has been assigned based on an analysis of crystal packing in the two forms and corroborated by inhibition studies with a synthetic peptide corresponding to the proposed docking position.
AB - The crystal structure of the nonheme iron-containing hydroxylase component of methane monooxygenase hydroxylase (MMOH) from Methylococcus capsulatus (Bath) has been solved in two crystal forms, one of which was refined to 1.7 Å resolution. The enzyme is composed of two copies each of three subunits (α2β2γ2), and all three subunits are almost completely α-helical, with the exception of two β hairpin structures in the (α subunit. The active site of each (α subunit contains one dinuclear iron center, housed in a four-helix bundle. The two iron atoms are octahedrally coordinated by 2 histidine and 4 glutamic acid residues as well as by a bridging hydroxide ion, a terminal water molecule, and at 4°C, a bridging acetate ion, which is replaced at -160°C with a bridging water molecule. Comparison of the results for two crystal forms demonstrates overall conservation and relative orientation of the domain structures. The most prominent structural difference identified between the two crystal forms is in an altered side chain conformation for Leu 110 at the active site cavity. We suggest that this residue serves as one component of a hydrophobic gate controlling access of substrates to and products from the active site. The leucine gate may be responsible for the effect of the B protein component on the reactivity of the reduced hydroxylase with dioxygen. A potential reductase binding site has been assigned based on an analysis of crystal packing in the two forms and corroborated by inhibition studies with a synthetic peptide corresponding to the proposed docking position.
KW - Dinuclear iron center
KW - Leucine gate
KW - Nonheme iron enzyme
KW - Protein crystallography
KW - Reductase binding site
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U2 - 10.1002/(SICI)1097-0134(199710)29:2<141::AID-PROT2>3.0.CO;2-G
DO - 10.1002/(SICI)1097-0134(199710)29:2<141::AID-PROT2>3.0.CO;2-G
M3 - Article
C2 - 9329079
AN - SCOPUS:0030885887
VL - 29
SP - 141
EP - 152
JO - Proteins: Structure, Function and Genetics
JF - Proteins: Structure, Function and Genetics
SN - 0887-3585
IS - 2
ER -