TY - JOUR TI - Interactions between a subset of substrate side chains and AAA+ motor pore loops determine grip during protein unfolding AU - Bell, Tristan A AU - Baker, Tania A AU - Sauer, Robert T A2 - Brunger, Axel T A2 - Kuriyan, John A2 - Lander, Gabriel C VL - 8 PY - 2019 DA - 2019/06/28 SP - e46808 C1 - eLife 2019;8:e46808 DO - 10.7554/eLife.46808 UR - https://doi.org/10.7554/eLife.46808 AB - Most AAA+ remodeling motors denature proteins by pulling on the peptide termini of folded substrates, but it is not well-understood how motors produce grip when resisting a folded domain. Here, at single amino-acid resolution, we identify the determinants of grip by measuring how substrate tail sequences alter the unfolding activity of the unfoldase-protease ClpXP. The seven amino acids abutting a stable substrate domain are key, with residues 2–6 forming a core that contributes most significantly to grip. ClpX grips large hydrophobic and aromatic side chains strongly and small, polar, or charged side chains weakly. Multiple side chains interact with pore loops synergistically to strengthen grip. In combination with recent structures, our results support a mechanism in which unfolding grip is primarily mediated by non-specific van der Waal’s interactions between core side chains of the substrate tail and a subset of YVG loops at the top of the ClpX axial pore. KW - ClpXP KW - AAA+ enzymes KW - ATP-dependent protein unfolding KW - protein degradation JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -