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PDBsum entry 2gsz
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Protein transport
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PDB id
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2gsz
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References listed in PDB file
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Key reference
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Title
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Crystal structures of the pilus retraction motor pilt suggest large domain movements and subunit cooperation drive motility.
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Authors
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K.A.Satyshur,
G.A.Worzalla,
L.S.Meyer,
E.K.Heiniger,
K.G.Aukema,
A.M.Misic,
K.T.Forest.
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Ref.
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Structure, 2007,
15,
363-376.
[DOI no: ]
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PubMed id
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Abstract
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PilT is a hexameric ATPase required for bacterial type IV pilus retraction and
surface motility. Crystal structures of ADP- and ATP-bound Aquifex aeolicus PilT
at 2.8 and 3.2 A resolution show N-terminal PAS-like and C-terminal RecA-like
ATPase domains followed by a set of short C-terminal helices. The hexamer is
formed by extensive polar subunit interactions between the ATPase core of one
monomer and the N-terminal domain of the next. An additional structure captures
a nonsymmetric PilT hexamer in which approach of invariant arginines from two
subunits to the bound nucleotide forms an enzymatically competent active site. A
panel of pilT mutations highlights the importance of the arginines, the PAS-like
domain, the polar subunit interface, and the C-terminal helices for retraction.
We present a model for ATP binding leading to dramatic PilT domain motions,
engagement of the arginine wire, and subunit communication in this hexameric
motor. Our conclusions apply to the entire type II/IV secretion ATPase family.
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Figure 3.
Figure 3. Conserved Elements of PilT Fold
(A) The NTD of
PilT (colored as in Figure 2A) resembles the well-known PAS
domain (gray, represented by the circadian clock protein Period;
Yildiz et al., 2005). Noncanonical PAS elements (PilT αA and
loops within Period) are removed for clarity.
(B) The core
ATPase subdomain of PilT (green) is readily superimposable upon
RecA (Story and Steitz, 1992) (gray). In this view, the
least-squares calculation is over P-loop residues only. Type
II/IV secretion ATPase family motifs Walker A (blue), Asp box
(lime green), Walker B (magenta), and His box (orange) neighbor
the bound nucleotide.
(C) Isolated, magnified view of the
four sequence motifs described in (B), with ATP and signature
invariant residues Lys149, Glu176, Glu217, and His242 depicted
(blue, green, magenta, and orange, respectively).
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Figure 8.
Figure 8. Model for Concerted PilT Motions
(A) The
quasi-two-fold symmetric C2 crystal structure has two peripheral
wide-open subunits (B, E; blue), two central “active”
subunits (C, F; orange), and two central “resting” subunits
(A, D; green). Four CTD:CTD interfaces are engaged (double
lines). The remaining two are disengaged (zig-zag). Subunit F is
clamped around bound nucleotide.
(B) When ATP (red) binds
in the E cleft, the two domains close around the ligand (short
black arrows), causing the β5/β6 arginines to approach the
ATP. Because of the extensive CTD[D]:NTD[E] interface, the
motion of NTD[E] forces the swiveling of CTD[D](in particular
the C-terminal helices) toward the periphery of the hexamer
(long gray arrow). Consequently, the D arginine fingers approach
the E active site (double lines). On the other side of CTD[D],
the interface likewise rearranges, disengaging CTD[C] from the D
active site (zig-zag).
(C) Subunit D is now poised as the
most peripheral, wide-open subunit and ready to bind nucleotide;
E is clamped around nucleotide and contributing to an engaged
CTD:CTD interface on either side.
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The above figures are
reprinted
from an Open Access publication published by Cell Press:
Structure
(2007,
15,
363-376)
copyright 2007.
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