Structural heterogeneity in microcrystalline ubiquitin studied by solid-state NMR
 

Structural heterogeneity in microcrystalline ubiquitin studied by solid-state NMR

Abstract

By applying [1-13C]- and [2-13C]-glucose labeling schemes to the folded globular protein ubiquitin, a strong reduction of spectral crowding and increase in resolution in solid-state NMR (ssNMR) spectra could be achieved. This allowed spectral resonance assignment in a straightforward manner and the collection of a wealth of long-range distance information. A high precision solid-state NMR structure of microcrystalline ubiquitin was calculated with a backbone rmsd of 1.57 to the X-ray structure and 1.32 Å to the solution NMR structure. Interestingly, we can resolve structural heterogeneity as the presence of three slightly different conformations. Structural heterogeneity is most significant for the loop region ?1-?2 but also for ?-strands ?1, ?2, ?3, and ?5 as well as for the loop connecting ?1 and ?3. This structural polymorphism observed in the solid-state NMR spectra coincides with regions that showed dynamics in solution NMR experiments on different timescales.




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