Figure 1.

Global motions of the HER2 structures as determined by the results of PCA. The structures represent displacements along the first eigenmode for (A) the Y877-unphosphorylated active system, (B) the Y877-unphosphorylated inactive system, (C) the Y877-phosphorylated active system, and (D) the Y877-phosphorylated inactive system. The structures are color-coded according to the RMSD (red and white indicate large fluctuations, blue indicates smaller fluctuations) to illustrate the motions in individual residues. The four key domains move in a concerted manner in the active system, whereas the inactive system lacks such correlated fluctuations.