FIG. 2.

Types of interaction between Vav and upstream elements during the signaling of membrane PTKs (A), cytokine receptors (B), the TCRαβ (C), and the BCR (D). PTK, protein tyrosine kinase; L, ligand; Ag, antigen; KD, kinase domain; P, phosphorylated tyrosine residue; N, proximal SH3 domain; C, distal SH3 domain. Transmembrane domains are indicated by open boxes, immunoreceptor tyrosine-based activation motif-containing molecules are shown as boxes with horizontal lines, SH2 domains are shown as solid boxes, SH3 domains are shown as dotted circles, and the rest of the N-terminal domains of Vav are shown as a shaded box. The proteins included are not shown to scale. The two possible transmembrane ligands for CD28 (CD80 and CD86) are indicated. The ligand for CD19 is as yet unknown, although it is believed that it binds to complement (C3) with the help of a second coreceptor, CD21 (43).