Protein–protein interaction domains involved in insulin signal transduction. A typical IRS protein contains a PH domain, which targets the protein in plasma membrane, and a PTB domain, which binds to NPXpY motif in the β subunit of the insulin receptor. SH2 domains of SH2 adaptors and SH2 enzymes bind to multiple phosphotyrosines of IRS proteins. SH2 adaptors frequently possess SH3 domains that recognize PXXP motifs of other intracellular proteins, leading to further downstream signal transduction.