 |
PDBsum entry 1xwi
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Protein transport
|
PDB id
|
|
|
|
1xwi
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structural and mechanistic studies of vps4 proteins.
|
|
|
Authors
|
|
A.Scott,
H.Y.Chung,
M.Gonciarz-Swiatek,
G.C.Hill,
F.G.Whitby,
J.Gaspar,
J.M.Holton,
R.Viswanathan,
S.Ghaffarian,
C.P.Hill,
W.I.Sundquist.
|
|
|
Ref.
|
|
EMBO J, 2005,
24,
3658-3669.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
VPS4 ATPases function in multivesicular body formation and in HIV-1 budding.
Here, we report the crystal structure of monomeric apo human VPS4B/SKD1
(hVPS4B), which is composed of five distinct elements: a poorly ordered
N-terminal MIT domain that binds ESCRT-III substrates, large (mixed alpha/beta)
and small (alpha) AAA ATPase domains that closely resemble analogous domains in
the p97 D1 ATPase cassette, a three-stranded antiparallel beta domain inserted
within the small ATPase domain, and a novel C-terminal helix. Apo hVPS4B and
yeast Vps4p (yVps4p) proteins dimerized in solution, and assembled into larger
complexes (10-12 subunits) upon ATP binding. Human and yeast adaptor proteins
(LIP5 and yVta1p, respectively) bound the beta domains of the fully assembled
hVPS4B and yVps4p proteins. We therefore propose that Vps4 proteins cycle
between soluble, inactive low molecular weight complexes and active,
membrane-associated double-ring structures that bind ATP and coassemble with
LIP5/Vta1. Finally, HIV-1 budding was inhibited by mutations in a loop that
projects into the center of the modeled hVPS4B rings, suggesting that hVPS4B may
release the assembled ESCRT machinery by pulling ESCRT-III substrates up into
the central pore.
|
|
|
|
|
|
|
|
Figure 1.
Figure 1 Structure of hVPS4B. (A) Domain map and numbering
scheme for hVPS4B. The domain color coding scheme shown here is
also used in Figures 2A, B, and 6. (B) Ribbon diagram
(stereoview) of the hVPS4B[123-444] structure. Note that the
 2/
 3
and 3/
4
loops were not defined by experimental density (dashed lines).
|
|
Figure 6.
Figure 6 Model for the functional cycle of VPS4 proteins. Left:
At steady state, hVPS4B is primarily a monomeric cytoplasmic
protein (Fujita et al, 2004), and exhibits a monomer-dimer
equilibrium in the absence of bound nucleotide (Babst et al,
1998; Supplementary Figure S3). LIP5/Vta1p is an oligomer of
uncertain stoichiometry. Middle: Vps4 proteins are recruited to
sites of vesicle formation at the endosomal membrane by
interactions between the N-terminal MIT domain and the
C-proximal domains of assembled ESCRT-III lattice/cage (Babst et
al, 2002; Lin et al, 2005; Scott et al, 2005). The assembled
Vps4 proteins can also bind ATP and LIP5/Vta1p oligomers via
domain
interactions to form an enzymatically active complex. Note that
a head-to-tail orientation of the two Vps4 rings (not shown) is
equally consistent with our data. Right: We propose that bound
ESCRT-III subunits are freed from the assembled lattice/cage and
released into the cytoplasm as they are pulled up into the
narrow central chamber of the hVPS4B ring.
|
|
|
|
|
|
The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
EMBO J
(2005,
24,
3658-3669)
copyright 2005.
|
|
|
|
|
|
|
