A C2 domain is a protein structural domain involved in targeting proteins to cell membranes. The typical version (PKC-C2) has a beta-sandwich composed of 8 beta-strands that co-ordinates two or three calcium ions, which bind in a cavity formed by the first and final loops of the domain, on the membrane binding face. The C2 domain of PRKCQ, the closest relative of PRKCQ in the PKC family, was found to be a novel Tyr(P)-binding domain, which could specifically bind a Tyr(P)-containing peptide derived from CDCP1, a protein known to be phosphorylated on tyrosine by activated Src kinase (1).

Reference
1. Stahelin, R.V. (2012) PRKCQ C2 domain is a phosphotyrosine binding module that plays a key role in its activation . J Biol Chem, 287, 30518-28. PMID: 22787157

    RKIP contains a novel phospho-amino acid binding domain. Substitutions in the ligand binding site of RKIP compromise the stability of the phosphorylated Raf-RKIP complex. Notably, PKM2 binds directly and selectively to tyrosine (Tyr, Y)-phosphorylated peptides, and expression of the phosphotyrosine-binding form of PKM2 is required for the rapid growth of cancer cells (1).
1. Kaneko T, Joshi R, Li SS. (2012) Phosphotyrosine recognition domains: the typical, the atypical and the versatile. Cell Commun Signal, 10(1), 32. PMID: 23134684

    The phosphotyrosine-binding (PTB) or phosphotyrosine interaction domain (PID) was originally identified in the protein, Shc, as a domain that could bind tyrosine-phosphorylated growth factor receptors. It was the second domain found to bind phosphotyrosine-containing peptides, having been preceded by the discovery of the Src homology 2 (SH2) domain several years earlier. Proteins with this domain are involved in diverse cellular functions, ranging from receptor signaling to protein targeting (1).

Reference
1. Zeng, L. (2014) Structural insights into FRS2 PTB domain recognition by neurotrophin receptor TrkB. Proteins, 82, 1534-41. PMID: 24470253

    The SH2 (Src Homology 2) domain is a structurally conserved protein domain contained within the Src and in many other intracellular signal-transducing proteins. SH2 domains allow proteins containing those domains to dock to phosphorylated tyrosine residues on other proteins. SH2 domains are commonly found in adapter proteins that aid in the signal transduction of receptor tyrosine kinase pathways. The yeast genome encodes only one SH2 domain-containing protein, the transcription factor Spt6. Recent study demonstrated that the Spt6 SH2 domain region can binds to Ser-phosphorylated CTD (1).

Reference
1. Kaneko, T. (2012) Phosphotyrosine recognition domains: the typical, the atypical and the versatile. Cell Commun Signal, 10, 32. PMID: 23134684