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Armadillo
repeat: A core region composed of 12 copies of a 42
amino acid sequence motif (residues 138-664) (Huber).
N-terminal:The primary
structure of b-catenin consist of an NH2-terminal portion of
approximately 130 amino acids(126-138 shown).The N-terminal
connects b-catenin/E-cadheren complex to a a-catenin - key
regulator of the actin cytoskeleton.
Four serine/threonine residues (S33,
S37, T41 and S45) at this region are well conserved
and conform to the consensus GSK-3
phosphorylation
site. The phosho-S/T residues are critical of b-catenin
recognitin by the F box protein B-Trcp
ubiquitin ligase.
The
first amino acid residues of the b-catenin C-terminal domain
is referred as Helix
C (residues 667-683). The Helix C (Leu673,
Leu677, Leu681) packs against otherwise
exposed hydrophobic residues from the last armadillo repeat,
capping the c-terminal of the b-catenin main core. Lys671
and Arg684 attach to
armadillo repeats through hydrogen bonds.
Helix C is
important for the transactivation domain of Wnt-responsive
genes, but not the turnover ob b-catenin through APC and cell
adhesion through cadherens.
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