Fig. 1: Model for substrate unfolding and translocation in the ATPase motor.
From: Nonequilibrium chemomechanical transduction of ATP-driven protein unfolding in the 26S proteasome
a Cartoon for the structure of the human proteasome and a top view of the ATPase motor composed of six RPT subunits denoted in different colors. H31 is the motor conformation with six substrate-engaged RPTs and closed interfaces. b Schema of state changes of the ATPase motor, including nucleotide changes caused by ATP (also ADP) binding and hydrolysis in the nucleotide-binding pocket, and conformational changes of the RPT complex. c Five types of motor conformations, represented by conformations H1, H2, H3, H4, and H5, considered in our model (left column), and the possible conformations they can transition to in a single next-step change (right column). The distances moved by the substrate as a result of the conformation change are also given, with one step equal to the length of two amino acids. The full list of motor conformations with substrate-disengaged RPT(s), from H1 to H30, is given in Fig. S1. In each conformation, the disengagement of an RPT from the substrate is represented by a displacement of RPT away from the central red dot, and the open interface between adjacent RPTs is represented by a gap.
