Cytoplasmic protein NCK2 (also known as NCK-beta and Grb4) is a protein encoded by the NCK2 gene. NCK belongs to family of adaptor proteins,There are two mammalian NCK genes, NCK1 and NCK2. NCK1 is located in chromosome 3 and NCK2 is located in chromosome 2. The protein contains three SH3 domains and one SH2 domain. The protein has no known catalytic function but has been shown to bind and recruit various proteins involved in the regulation of receptor protein tyrosine kinases.