title: High-Pressure NMR Spectroscopy Reveals Functional Sub-states of Ubiquitin and Ubiquitin-Like Proteins.
abstract: High-pressure nuclear magnetic resonance (NMR) spectroscopy has revealed that ubiquitin has at least two high-energy states--an alternatively folded state N2 and a locally disordered state I--between the basic folded state N1 and totally unfolded U state. The high-energy states are conserved among ubiquitin-like post-translational modifiers, ubiquitin, NEDD8, and SUMO-2, showing the E1-E2-E3 cascade reaction. It is quite intriguing that structurally similar high-energy states are evolutionally conserved in the ubiquitin-like modifiers, and the thermodynamic stabilities vary among the proteins. To investigate atomic details of the high-energy states, a Q41N mutant of ubiquitin was created as a structural model of N2, which is 71% populated even at atmospheric pressure. The convergent structure of the "pure" N2 state was obtained by nuclear Overhauser effect (NOE)-based structural analysis of the Q41N mutant at 2.5 kbar, where the N2 state is 97% populated. The N2 state of ubiquitin is closely similar to the conformation of the protein bound to the ubiquitin-activating enzyme E1. The recognition of E1 by ubiquitin is best explained by conformational selection rather than by induced-fit motion.
authors.affiliation: College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga, 525-8577, Japan, ryo@ph.ritsumei.ac.jp.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kitahara
mesh_terms: D001274:Atmospheric Pressure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D017510:Protein Folding; D025801:Ubiquitin / Q000737:chemistry*
chemical_list: D025801:Ubiquitin