The phosphotyrosine signaling circuitry of Ac. (a) Phosphotyrosine signaling is modulated by the writers (PTKs), erasers (PTPs) and readers (Src homology 2 (SH2); phosphotyrosine binding (PTB)). (b) The total number of PTKs, classical PTPs (total PTPs) and SH2 encoded genes across multiple eukaryote genomes. Highlighted in yellow are branches that compose a complete phosphotyrosine signaling circuit. The branched divergence times and lengths in millions of years (mya) are indicated. (c) The percentage of the genome devoted to encoding PTKs and SH2 domains. (d) Ac displays the greatest ratio of SH2:PTKs compared to other eukaryotes.