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PDBsum entry 2afh
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Oxidoreductase
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PDB id
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2afh
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Contents |
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476 a.a.
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522 a.a.
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289 a.a.
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References listed in PDB file
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Key reference
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Title
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Nitrogenase complexes: multiple docking sites for a nucleotide switch protein.
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Authors
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F.A.Tezcan,
J.T.Kaiser,
D.Mustafi,
M.Y.Walton,
J.B.Howard,
D.C.Rees.
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Ref.
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Science, 2005,
309,
1377-1380.
[DOI no: ]
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PubMed id
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Abstract
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Adenosine triphosphate (ATP) hydrolysis in the nitrogenase complex controls the
cycle of association and dissociation between the electron donor adenosine
triphosphatase (ATPase) (Fe-protein) and its target catalytic protein
(MoFe-protein), driving the reduction of dinitrogen into ammonia. Crystal
structures in different nucleotide states have been determined that identify
conformational changes in the nitrogenase complex during ATP turnover. These
structures reveal distinct and mutually exclusive interaction sites on the
MoFe-protein surface that are selectively populated, depending on the Fe-protein
nucleotide state. A consequence of these different docking geometries is that
the distance between redox cofactors, a critical determinant of the
intermolecular electron transfer rate, is coupled to the nucleotide state. More
generally, stabilization of distinct docking geometries by different nucleotide
states, as seen for nitrogenase, could enable nucleotide hydrolysis to drive the
relative motion of protein partners in molecular motors and other systems.
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Figure 2.
Fig. 2. nf-, pcp-, adp-, and alf-[4Fe:4S]-cluster positions
relative to the P-cluster and FeMo-cofactor as viewed
perpendicular (A) and parallel (B) to the local two-fold axis
relating an  ß pair of
Av1 subunits. The approximate distances shown in the side-view
(A) are between the cluster centroids (see also Table 1). The
centroid distance between the P-cluster and the FeMo-cofactor is
19.3 Å. The corresponding edge-to-edge [4Fe:4S]-P-cluster
distances between the nearest pair of atoms in these structures
are  5 Å shorter.
The outline of the Av1 surface is shown in coral.
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Figure 3.
Fig. 3. Schematic representation of Av1-Av2 docking geometry at
different nucleotide states. The species representing the
pcp-conformer (dotted lines) is included in both cartoons to
illustrate the relative docking positions of Av2 molecules.
Taking a reference point near the "top" surface of Av2 (away
from the interface with Av1) that is positioned on the two-fold
axis at a distance of 35 Å from the [4Fe:4S] cluster of
each Av2 dimer (point A: pcp-Av2; point B: nf-Av2; point C,
adp-Av2), the displacement between pcp-Av2 and nf-Av2 is 19
Å, and that between pcp-Av2 and the four adp-conformers
ranges from 10 to 23 Å.
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The above figures are
reprinted
by permission from the AAAs:
Science
(2005,
309,
1377-1380)
copyright 2005.
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