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PDBsum entry 2cjs
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References listed in PDB file
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Key reference
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Title
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Structural basis for a munc13-1 homodimer to munc13-1/rim heterodimer switch.
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Authors
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J.Lu,
M.Machius,
I.Dulubova,
H.Dai,
T.C.Südhof,
D.R.Tomchick,
J.Rizo.
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Ref.
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Plos Biol, 2006,
4,
e192.
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PubMed id
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Abstract
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C(2) domains are well characterized as Ca(2+)/phospholipid-binding modules, but
little is known about how they mediate protein-protein interactions. In neurons,
a Munc13-1 C(2)A-domain/RIM zinc-finger domain (ZF) heterodimer couples synaptic
vesicle priming to presynaptic plasticity. We now show that the Munc13-1 C(2)A
domain homodimerizes, and that homodimerization competes with Munc13-1/RIM
heterodimerization. X-ray diffraction studies guided by nuclear magnetic
resonance (NMR) experiments reveal the crystal structures of the Munc13-1
C(2)A-domain homodimer and the Munc13-1 C(2)A-domain/RIM ZF heterodimer at 1.44
A and 1.78 A resolution, respectively. The C(2)A domain adopts a beta-sandwich
structure with a four-stranded concave side that mediates homodimerization,
leading to the formation of an eight-stranded beta-barrel. In contrast,
heterodimerization involves the bottom tip of the C(2)A-domain beta-sandwich and
a C-terminal alpha-helical extension, which wrap around the RIM ZF domain. Our
results describe the structural basis for a Munc13-1 homodimer-Munc13-1/RIM
heterodimer switch that may be crucial for vesicle priming and presynaptic
plasticity, uncovering at the same time an unexpected versatility of C(2)
domains as protein-protein interaction modules, and illustrating the power of
combining NMR spectroscopy and X-ray crystallography to study protein complexes.
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Secondary reference #1
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Title
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A munc13/rim/rab3 tripartite complex: from priming to plasticity?
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Authors
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I.Dulubova,
X.Lou,
J.Lu,
I.Huryeva,
A.Alam,
R.Schneggenburger,
T.C.Südhof,
J.Rizo.
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Ref.
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EMBO J, 2005,
24,
2839-2850.
[DOI no: ]
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PubMed id
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Figure 5.
Figure 5 Models of the interactions of RIM2  with
Munc13-1 and Rab3A. RIM NT: -RIM
N-terminal sequence; Munc13 NT: Munc13-1 N-terminal sequence;
ZF: -RIM
ZF domain. The positions of the two -helices
(a1 and 2) and the SGAWFY motif are modeled according to the
crystal structure of the rabphilin/Rab3A complex (Ostermeier and
Brunger, 1999). Note that the helices may not be completely
structured in the absence of Rab3A. A star indicates the
approximate location of the mutation that disrupts Munc13-1
binding.
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Figure 6.
Figure 6 The RIM2 ZF
domain contains exposed, selectively conserved sequences that
may be involved in protein -protein interactions. (A) Sequence
alignment of the ZF domains from -RIMs,
rabphilin, and related Rab effectors. The sequences were
classified into four groups based on the sequence conservation
of their entire N-terminal fragments and a phylogenetic tree
created using VectorNTI (InforMax). The eight cysteines
conserved in all proteins are shown in white on a black
background. Identical or highly homologous (K=R, E=D, L=I=V)
residues that are selectively conserved in one group (appear in
>80% of group sequences), but may partially propagate into
another group, are shown on different backgrounds: RIMs--red,
rabphilins/NOCs--green, melanophilin/MyRIP--yellow, and
granuphilins/Slp5/Slp3--blue. Hs, Homo sapiens; Rn, Rattus
norvegicus; Tn, Tetraodon nigroviridis; Dm, Drosophila
melanogaster; Am, Apis mellifera; Ce, Caenorhabditis elegans;
Mm, Mus musculus; Xt, Xenopus tropicalis; Xl, Xenopus laevis;
Gg, Gallus gallus. (B) Ribbon diagram of the RIM2 ZF
domain. Loops are labeled L1 -L5,  -strands
are labeled b1 -b4, and the C-terminal helix is labeled a2. The
zinc ions are represented by yellow spheres. (C) Trace
superposition of the ZF domains from rabphilin (blue) and RIM2
(orange).
The N-terminus and the two N-terminal loops, which are most
divergent in the two structures, are labeled. (D) Space-filling
model of the RIM2 ZF
domain. The atoms from the loop1 -loop2 and b3 -loop5 sequences
that are selectively conserved in -RIMs
are colored in yellow and orange. The residues selected for
mutagenesis (in yellow) are labeled in (D) and are indicated by
a '*' in (A).
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The above figures are
reproduced from the cited reference
with permission from Macmillan Publishers Ltd
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