Grb-2

Grb-2 stands for growth factor receptor bound protein 2, is an adaptor protein fuond in humans. This adaptor protein is also present in the RAS signalling pathway. What it does is that it bind to the receptor tyrosine kinase (Grb2 has an SH2 domain), which then binds the GEF, which causes the release of GDP by RAS (RAS is a monomeric G-protein), which then takes up GTP, causing activation, which in turn delivers the signal on to other kinases.