Noncovalent dimerization of ubiquitin.
Bottom Line: Another kind of dynamics: Ubiquitin noncovalently dimerizes with a dissociation constant of approximately 5 mM.The two subunits adopt an array of relative orientations, utilizing an interface also for binding to other proteins (see picture).Quaternary fluctuation among members of the dimer ensemble constitutes a different kind of dynamics that complements the tertiary dynamics of each ubiquitin subunit.
Affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China.Show MeSH
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Mentions: Secondly, a covalent linkage may restrict the relative movement for the two adjacent subunits in a poly(ubiquitin), and select a subset of conformers from the ensemble structure of the non-covalent dimer. Indeed, the crystal structure of Lys48-linked di-ubiquitin falls into the boundary of the atomic probability map delineated by the noncovalent dimer (Figure 5a). The noncovalent dimer, however, encompasses more interfacial residues than the Lys-48 linked covalent dimer—residues 4–7, 10–12, and 62–66 that are part of the dimer interface in the former become solvent-exposed in the latter (Figure 5b). Interestingly, these residues are also involved in interactions with certain UBDs20a–d and may permit the initial latching in respective binding processes.
Affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China.