Figure 1.

The auxilin J-domain/ATPase interface. (A) Summary of residues determined to be involved in ATPase/J-domain interaction by mutation (red and yellow) and NMR (pink). The J-domain of auxilin is shown on the left, and the ATPase domain on the right, with the interaction interface surfaces of both proteins facing the viewer. The two red residues are a rescue mutant pair; function lost by the D35N J-domain mutation is restored by a R171H ATPase mutation in the bacterial DnaK/DnaJ system (Gässler et al. 1998). ATPase residue D206, critical for the ATP-induced conformational change of Hsp70 and part of the ATPase active site cleft, is also shown. Residues whose mutation did not affect interaction are shown in dark gray. The J-domain residue numbers correspond to DnaJ except for K847, which is unique to auxilin. (B) Electrostatic potential surfaces at the ATPase/J-domain interface. Blue represents positive potential; red, negative. The J-domain “positive patch” corresponds to the prominent blue area on the auxilin J-domain surface. The ATPase domain acidic region corresponds to the red area to the left and in the bottom portion of the “lower cleft,” seen running vertically through the middle of the ATPase surface in this view.