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PDBsum entry 1l7c
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Cell adhesion
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PDB id
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1l7c
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Biochemical and structural definition of the l-Afadin- And actin-Binding sites of alpha-Catenin.
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Authors
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S.Pokutta,
F.Drees,
Y.Takai,
W.J.Nelson,
W.I.Weis.
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Ref.
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J Biol Chem, 2002,
277,
18868-18874.
[DOI no: ]
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PubMed id
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Abstract
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alpha-Catenin is an integral component of adherens junctions, where it links
cadherins to the actin cytoskeleton. alpha-Catenin is also required for the
colocalization of the nectin/afadin/ponsin adhesion system to adherens
junctions, and it specifically associates with the nectin-binding protein
afadin. A proteolytic fragment of alpha-catenin, residues 385-651, contains the
afadin-binding site. The three-dimensional structure of this fragment comprises
two side-by-side four-helix bundles, both of which are required for afadin
binding. The alpha-catenin fragment 385-651 binds afadin more strongly than the
full-length protein, suggesting that the full-length protein harbors a cryptic
binding site for afadin. Comparison of the alpha-catenin 385-651 structure with
the recently solved structure of the alpha-catenin M-fragment (Yang, J.,
Dokurno, P., Tonks, N. K., and Barford, D. (2001) EMBO J. 20, 3645-3656) reveals
a surprising flexibility in the orientation of the two four-helix bundles.
alpha-Catenin and the actin-binding protein vinculin share sequence and most
likely structural similarity within their actin-binding domains. Despite this
homology, actin binding requires additional sequences adjacent to this region.
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Figure 2.
Fig. 2. Oligomerization of  -catenin
385-651 and its N- and C-terminal subdomains. Fragments at the
indicated concentrations were incubated with a 30-fold excess of
cross-linker. For the two amine-reactive cross-linking reagents
BS3 and DMS with spacer arms of 11.4 and 11.0 Å,
respectively, different cross-linking efficiency was observed.
Higher cross-linking efficiency results are shown here and were
obtained with DMS in the case of -catenin
507-632 and BS3 for -catenin
385-651 and -catenin
385-507. The first lane for the -catenin
385-651 fragment shows a sample in the absence of cross-linker.
Molecular mass markers are indicated on the left of each gel,
and apparent molecular mass of the fragments and cross-linking
products are shown on the right.
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Figure 4.
Fig. 4. Interaction of -catenin (
-cat) with
F-actin. A, schematic representation of -catenin
and the constructs used in the binding assay. Vinculin homology
regions are shown in dark gray. B, binding to F-actin was
examined by cosedimentation. Assuming a binding ratio of
protein:monomeric actin of 1:7, all -catenin
constructs were added in excess. The supernatant (S) containing
the unbound protein and the pellet (P) containing F-actin and
bound protein are shown for each sample. Molecular mass markers
are indicated on the left.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
18868-18874)
copyright 2002.
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