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PDBsum entry 2zn9
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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 ca2+ -Dependent formation of alg-2/alix peptide complex: ca2+/ef3-Driven arginine switch mechanism.
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Authors
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H.Suzuki,
M.Kawasaki,
T.Inuzuka,
M.Okumura,
T.Kakiuchi,
H.Shibata,
S.Wakatsuki,
M.Maki.
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Ref.
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Structure, 2008,
16,
1562-1573.
[DOI no: ]
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PubMed id
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Abstract
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ALG-2 belongs to the penta-EF-hand (PEF) protein family and interacts with
various intracellular proteins, such as Alix and TSG101, that are involved in
endosomal sorting and HIV budding. Through X-ray crystallography, we solved the
structures of Ca(2+)-free and -bound forms of N-terminally truncated human ALG-2
(des3-20ALG-2), Zn(2+)-bound form of full-length ALG-2, and the structure of the
complex between des3-23ALG-2 and the peptide corresponding to Alix799-814 in
Zn(2+)-bound form. Binding of Ca(2+) to EF3 enables the side chain of Arg125,
present in the loop connecting EF3 and EF4, to move enough to make a primary
hydrophobic pocket accessible to the critical PPYP motif, which partially
overlaps with the GPP motif for the binding of Cep55 (centrosome protein 55
kDa). Based on these results, together with the results of in vitro binding
assay with mutant ALG-2 and Alix proteins, we propose a Ca(2+)/EF3-driven
arginine switch mechanism for ALG-2 binding to Alix.
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Figure 1.
Figure 1. Schematic Representations of ALG-2 and Alix
Human ALG-2 has a Gly/Pro-rich N-terminal region followed by the
PEF domain containing five EF-hands (EF1–EF5) with eight α
helices (α1–α8). The first and second helices in each EF
hand are alternatively named, for instance, helix E1 and helix
F1, respectively. An alternatively spliced isoform (lacking
Gly121-Phe122) is designated ALG-2^ΔGF122 in this article.
Recombinant proteins of full-length ALG-2 and two types of
N-terminal deletion mutants (des3-20ALG-2 and des3-23ALG-2) were
crystallized. Alix has three distinct domains, named Bro1, V,
and Pro-rich. A 16-mer synthetic oligopeptide of the ABS in Alix
(Alix ABS peptide) was used for cocrystallization.
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Figure 2.
Figure 2. Comparison of Ca^2+-Free and Ca^2+-Bound Forms and
Zn^2+-Bound Form of ALG-2
(A–C) Structures of EF1 (A),
EF3 (B), and EF5 (C) of Ca^2+-free form (cyan) and Ca^2+-bound
form (magenta) of des3-20ALG-2 and Zn^2+-bound form (green) of
full-length ALG-2 are superimposed and shown in ribbon
representation in side views and top views by aligning helices
of (A) α1 (E1), (B) α4 (E3), and (C) α7 (E5), respectively,
with the secondary structure matching program in COOT. Calcium
atoms and zinc atoms are shown as yellow spheres and gray
spheres, respectively.
(D) Overall structures of dimeric
ALG-2 molecules in the three forms are aligned at α7 of
molecule A and shown in wire presentation. The N-terminal
Gly/Pro-rich region is invisible.
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The above figures are
reprinted
by permission from Cell Press:
Structure
(2008,
16,
1562-1573)
copyright 2008.
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