The crystal structure of XC847 from Xanthomonas campestris: a 3'-5' oligoribonuclease of DnaQ fold family with a novel opposingly shifted helix

The mechanism by which ligand‐activated EGFR induces autophosphorylation via dimerization is not fully understood. Structural studies have revealed an extracellular loop mediated receptor dimerization. We have previously presented experimental data showing the involvement of a positive 13 amino acid peptide (R645–R657; P13⁺) from the intracellular juxtamembrane domain (JM) of EGFR important for intracellular dimerization and autophosphorylation. A model was presented that suggest that P13⁺ interacts with a negative peptide (D979–E991; P13^?) positioned distal to the tyrosine kinase domain in the opposite EGFR monomer. The present work shows additional data strengthening this model. In fact, by analyzing protein sequences of 21 annotated ErbB proteins from 9 vertebrate genomes, we reveal the high conservation of peptides P13⁺ and P13^? with regard to their sequence as well as their position relative to the tyrosine kinase (TK) domain. Moreover in silico structure modeling of these ErbB intracellular domains supports a general electrostatic P13⁺/P13^? interaction, implying that the C‐terminal of one receptor monomer is facing the TK domain of the other monomer in the receptor dimer and vice versa. This model provides new insights into the molecular mechanism of ErbB receptor activation and suggests a new strategy to pharmacologically interfering with ErbB receptor activity. Proteins 2006. © 2005 Wiley‐Liss, Inc.