Fig. 2: PA26E102A-Opt5 induces terminus-dependent activation and gate opening of the h20S.
From: The YΦ motif defines the structure-activity relationships of human 20S proteasome activators
a Schematic of how PA26’s activation loop (black cartoon) directly repositions the Pro17 reverse turn of the 20S α-subunit (gray cartoon) to induce HbYX-independent gate opening (PDB ID: 1YA7). b Stimulation of h20S by PA26 constructs: wild-type PA26 (wt, black), disabled-loop mutant (PA26E102A, red), and a disabled-loop mutant with C-terminal Opt5 (NLSYYT) sequence (PA26E102A-Opt5, blue). Data are normalized to PA26E102A-Opt5 and plotted individually (n = 3). Reported EC50 is a mean of EC50 values calculated from three independent experiments (n = 3) with error reported as s.e.m. KD values were determined by BLI from three independent experiments (n = 3) and reported as the mean ± s.e.m. c PA26E102A-Opt5 induces gate opening. The 3D reconstruction of the singly capped PA26E102A-Opt5-h20S complex at 2.9 Å resolution from 234,960 particles shows gate opening (blue box) relative to the apo, closed gate α-ring on the opposite side (red box).
