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PDBsum entry 3fxe
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Unknown function
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PDB id
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3fxe
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References listed in PDB file
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Key reference
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Title
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Structure and function of interacting icmr-Icmq domains from a type ivb secretion system in legionella pneumophila.
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Authors
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S.Raychaudhury,
J.D.Farelli,
T.P.Montminy,
M.Matthews,
J.F.Ménétret,
G.Duménil,
C.R.Roy,
J.F.Head,
R.R.Isberg,
C.W.Akey.
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Ref.
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Structure, 2009,
17,
590-601.
[DOI no: ]
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PubMed id
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Abstract
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During infection, Legionella pneumophila creates a replication vacuole within
eukaryotic cells and this requires a Type IVb secretion system (T4bSS). IcmQ
plays a critical role in the translocase and associates with IcmR. In this
paper, we show that the N-terminal domain of IcmQ (Qn) mediates
self-dimerization, whereas the C-terminal domain with a basic linker promotes
membrane association. In addition, the binding of IcmR to IcmQ prevents
self-dimerization and also blocks membrane permeabilization. However, IcmR does
not completely block membrane binding by IcmQ. We then determined crystal
structures of Qn with the interacting region of IcmR. In this complex, each
protein forms an alpha-helical hairpin within a parallel four-helix bundle. The
amphipathic nature of helices in Qn suggests two possible models for membrane
permeabilization by IcmQ. The Rm-Qn structure also suggests how IcmR-like
proteins in other L. pneumophila species may interact with their IcmQ partners.
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Figure 4.
Figure 4. Structure of an Rm-Qn Four-Helix Bundle
(A) A
rotation series of the Rm-Qn four-helix bundle is presented with
the molecules displayed as ribbons. This structure is from the
derivative crystals.
(B) Nonpolar side chains in the Rm-Qn
interface are shown as solid spheres and are color coded for
those from Qn (blue) and from Rm (tan).
(C) Side chains in
the Rm-Qn interface are shown as stick models with CPK colors
and are labeled.
(D) A top view is shown of the Rm-Qn
four-helix bundle with α helices displayed as ribbons and side
chains as CPK stick models. The figure was made with Chimera.
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Figure 6.
Figure 6. Qn α Helices are Amphipathic and Show a Charge
Segregation
(A) Qn α helices are shown in the context of
the Rm-Qn dimer (left) and dissected out from the helix bundle
(center and right). The Qn α helices are amphipathic with a
hydrophobic face (green arrows) and charged faces (blue arrow
for basic and red arrow for acidic).
(B) Helix wheel
diagrams for the two Qn α helices show the charge segregation
between the two α helices.
(C) A possible model is shown
for the Qn-Qn four-helix bundle that may mediate IcmQ
dimerization.
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The above figures are
reprinted
by permission from Cell Press:
Structure
(2009,
17,
590-601)
copyright 2009.
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