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PDBsum entry 2oap
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References listed in PDB file
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Key reference
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Title
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Hexameric structures of the archaeal secretion atpase gspe and implications for a universal secretion mechanism.
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Authors
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A.Yamagata,
J.A.Tainer.
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Ref.
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EMBO J, 2007,
26,
878-890.
[DOI no: ]
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PubMed id
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Abstract
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The secretion superfamily ATPases are conserved motors in key microbial membrane
transport and filament assembly machineries, including bacterial type II and IV
secretion, type IV pilus assembly, natural competence, and archaeal flagellae
assembly. We report here crystal structures and small angle X-ray scattering
(SAXS) solution analyses of the Archaeoglobus fulgidus secretion superfamily
ATPase, afGspE. AfGspE structures in complex with ATP analogue AMP-PNP and
Mg(2+) reveal for the first time, alternating open and closed subunit
conformations within a hexameric ring. The closed-form active site with bound
Mg(2+) evidently reveals the catalytically active conformation. Furthermore,
nucleotide binding results and SAXS analyses of ADP, ATPgammaS, ADP-Vi, and
AMP-PNP-bound states in solution showed that asymmetric assembly involves ADP
binding, but clamped closed conformations depend on both ATP gamma-phosphate and
Mg(2+) plus the conserved motifs, arginine fingers, and subdomains of the
secretion ATPase superfamily. Moreover, protruding N-terminal domain shifts
caused by the closed conformation suggest a unified piston-like, push-pull
mechanism for ATP hydrolysis-dependent conformational changes, suitable to drive
diverse microbial secretion and assembly processes by a universal mechanism.
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Figure 1.
Figure 1 AfGspE subunit structure. (A) Experimental electron
density (contoured at 1  )
overlaid with the final refined model. (B) AfGspE fold as
ribbons (molecule B) with subdomains N1 (yellow), N2 (green), C1
(blue), and C2 (magenta) plus bound AMP-PNP (red sticks), and
P-loop (orange, center). (C) Topology schematic, (D) C  stereo
diagram of two superimposed afGspE subunit structures with bound
AMP-PNP (red, CPK spheres). The open form (molecule A, orange)
needs NTD rotations to yield the closed form (molecule B, blue).
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Figure 3.
Figure 3 Hexameric ring structure, assembly, AMP-PNP binding,
alternating subunit conformations, and subunit interactions. (A)
AfGspE hexamer assembly and fold shown as ribbons and as
schematic shapes viewed from top and side. Bound AMP-PNP (red,
CPK spheres) in closed form molecules (blue, light blue NTD) and
alternate open form molecules (orange, light orange NTD). (B)
Electron micrograph of negatively stained AfGspE proteins with
AMP-PNP. Ring structures are indicated by black arrows. (C)
Subunit-subunit interactions with domain colors as in A, and
encircled residues for N2:C1 (red), for C1:C1 (green), and N1:C2
(magenta) interactions.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
EMBO J
(2007,
26,
878-890)
copyright 2007.
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