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Figure 1.
Figure 1. Primary Structure of Axin and APC(A) Axin. The
binding sites of partner proteins are indicated. RGS, regulator
of G protein signaling-homologous domain; DIX, dishevelled and
axin-interaction domain.(B) APC. The four β-catenin binding
15-mer repeats are shown as white boxes and labeled A–D, and
the seven 20-mer repeats (labeled 1–7) are shown as black
boxes. The three axin binding SAMP repeats are shown in gray.
Olig, dimerization domain; arm, armadillo repeat domain; basic,
basic region; dlg, Discs-large binding site.(C) Structure-based
alignment of the human APC β-catenin binding sequences. Residue
numbers are indicated. The standard alignments of the APC
repeats are highlighted in yellow to show the shift in register
revealed by the R3 complex structure. The “core homology
region” is the basis of the standard alignments. The shaded
region of R3 is observed in the nonphosphorylated structure. The
five residues that constitute the motif for interaction with
β-catenin arm repeats 5-9 are shown in red. The order of
CK1 and GSK-3β phosphorylation is indicated on the alignment.
The four serine residues visible in the structure are indicated
in blue, and the two others that represent the priming
phosphorylations are shown in green. The structure-based
alignment of the E-cadherin sequence is indicated, including the
locations of the three pSer residues (green boxes) observed in
the crystal structure of its complex with β-catenin (Huber and
Weis, 2001). The R6 sequence used in initial experiments is
underlined.
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