Abstract
Atomic-resolution structure determination is crucial for understanding protein function.Cryo-EM and NMR spectroscopy both provide structural information, but currently cryo-EMdoes not routinely give access to atomic-level structural data, and, generally, NMR structuredetermination is restricted to small (<30 kDa) proteins. We introduce an integrated structuredetermination approach that simultaneously uses NMR and EM data to overcome the limitsof each of these methods. The approach enables structure determination of the 468 kDalarge dodecameric aminopeptidase TET2 to a precision and accuracy below 1 Å by combiningsecondary-structure information obtained from near-complete magic-angle-spinning NMRassignments of the 39 kDa-large subunits, distance restraints from backbone amides and ILVmethyl groups, and a 4.1 Å resolution EM map. The resulting structure exceeds currentstandards of NMR and EM structure determination in terms of molecular weight and pre-cision. Importantly, the approach is successful even in cases where only medium-resolutioncryo-EM data are available