Generic phosphotyrosine-adaptor recruitment motif

The minimal, reusable receptor-proximal recruitment motif: an activated receptor (or receptor-associated kinase) presents a phosphotyrosine docking site; an SH2- or PTB-domain adaptor recognizes that phosphotyrosine; and the adaptor, through a second interaction surface (e.g. an SH3 domain), recruits a downstream effector to the membrane. This pTyr -> adaptor -> effector wiring is the generic interface by which receptor tyrosine kinases, cytokine-receptor- associated JAKs, and other tyrosine-phosphorylation events launch downstream pathways - it is the recruitment step that precedes the Ras switch in MODULE:erk_cascade. The motif is gene-free and taxon-neutral, fixing only the phosphotyrosine-binding and adaptor roles and the recruitment topology. Grounded in GO:0007169 (cell surface receptor protein tyrosine kinase signaling pathway).

Reusable conformance target. A node declares `conforms_to: [{template: phosphotyrosine_adaptor_recruitment}]` when a phosphotyrosine docking site recruits an SH2/PTB adaptor that in turn recruits a downstream effector. The specific adaptor (GRB2, SHC, ...) and effector are realization-specific.