STRONG HYDROGEN-BONDING INTERACTIONS INVOLVING A BURIED GLUTAMIC-ACIDIN THE TRANSMEMBRANE SEQUENCE OF THE NEU ERBB-2 RECEPTOR/

The receptor tyrosine kinase encoded by the neu/erbB-2 proto-oncogene is constitutively activated by a single valine to glutamic acid substi tution at position 664 in the predicted membrane-spanning sequence of the receptor. We have explored the structural changes involved in rece ptor activation with polarized FTIR and magic angle spinning NMR spect roscopy. The hydrophobic transmembrane sequence folds into a well-defi ned alpha-helical structure spanning the membrane bilayer. Measurement s of the pK(a) and C-13 chemical shift anisotropy of Glu 664 reveal th at the side chain carboxyl group is protonated and strongly hydrogen b onded. These studies provide direct evidence for glutamate hydrogen-bo nding interactions in the mechanism of receptor dimerization and activ ation.