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Figure 4.
Fig. 4. Comparison of the SH3 polyproline helix binding
site to the analogous region in MIA. (A) Superposition of the
conserved residues in the polyproline helix binding site of
Sem-5 (red) and the corresponding residues in MIA (blue). Four
of six residues conserved in SH3 domains differ in MIA. Residue
numbering corresponds to MIA. Residues listed in parentheses are
those found in canonical SH3 domains. (B) View of the molecular
surfaces of MIA (Left) and the Sem-5 SH3 domain (Right). The
structure of Sem-5 is shown with its polyproline ligand bound.
Sem-5 residues colored in red are those that make up a triad of
conserved aromatic residues arranged approximately linearly on
the molecular surface. The dissimilarity of the corresponding
residues in MIA, F59, I83, and Q28 result in a much smoother
molecular surface that most likely does not recognize
polyproline helices.
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