(A) Amino acid sequence and known motifs of pp135. The underlined amino acids are the SH2 domain, SH3 domain, 5-phosphatase conserved motifs, and proline-rich domain. The hatched-underlined amino acids are the two binding sites for PTB domain. The hatched-overlined amino acids are the six peptides obtained from the amino acid sequence of purified pp135. (B) Diagrammatic representation of the various domains within pp135.