The ErbB receptor tyrosine kinases govem major signaling pathways and their deregulation results in aggressive tumour growth.Developing efficient small agents towards these attractive targets located both in cytoplasm and nuclear membranes is difficult task because of the complexity of molecular interactions.Peptide ligand binding to the extracellular region triggers receptors autophosphorylation and downstream signal transduction via the kinase domain involved in interactions with cytoplasm and nuclear proteins.ErbBs participate also in lateral transactivation of different receptor tyrosine kinases.To search for molecules recognizing protein-protein interaction interface in ErbBs we used advantages of their domain organization to construct shortened protein probes.