Figure 1.

The worm and yeast SH3 domain peptide-binding specificity repertoire is conserved. SH3 domain specificities (36 worm, orange labels; 24 yeast, black labels), visualized as sequence logos, are grouped by similarity in a tree (see Experimental Procedures). Tree branches are colored according to their specificity class: I (red), II (blue), and atypical (black). Underlined labels indicate domains that exhibit multiple specificities. Multiple peptide libraries were used to determine specificity: X₆-PXXP-X₆ (*), X₆-PXXP-X₆ and X₁₂ (**), X₆-PXXP-X₆ and X₇-R/K-X₇ (***), or X₁₂ (no asterisk), where P is proline, R is arginine, K is lysine, and X is any amino acid (see Experimental Procedures).