The Src homology type 2 (SH2) domain is a highly conserved motif of about 100 amino acids which mediates protein-protein interactions by binding to phosphotyrosine. p56-lck, a T-cell-specific src family tyrosine kinase with an SH2 domain, is involved in T-cell signal transduction.

A 62-kD protein (p62) was identified by Park et al. (1995) as a ligand of the p56-lck SH2 domain. Gong et al. (1999) screened a yeast 2-hybrid library made from rat hippocampal mRNA against full-length Kv-beta-2 . Two previously unknown interacting proteins were identified, one of which was identical to Zip (PKC-zeta)-interacting protein), the rat homolog of p62. Zip1 and Zip2, which arise from alternative splicing, are identical except for 27 residues missing from Zip2.