17O NMR studies of yeast ubiquitin in aqueous solution and in the solid state.

We report a general method for amino acid-type specific 17 O-labeling of recombinant proteins in Escherichia coli. In particular, we have prepared several [1- 13 C, 17 O]-labeled yeast ubiquitin (Ub) samples including Ub-[1- 13 C, 17 O]Gly, Ub-[1- 13 C, 17 O]Tyr, and Ub-[1- 13 C, 17 O]Phe using the auxotrophic E. coli strain DL39 GlyA l DE3 ( asp C - tyr B - ilv E - gly A - l DE3). We have also produced Ub-[ h - 17 O]Tyr, where the phenolic group of Tyr59 is 17 O-labeled. We showed for the first time that 17 O NMR signals from protein terminal residues and sidechains can be readily detected in aqueous solution. We also reported solid-state 17 O NMR spectra for Ub-[1- 13 C, 17 O]Tyr and Ub-[1- 13 C, 17 O]Phe obtained at an ultrahigh magnetic field, 35.2 T (1.5 GHz for 1 H). This work represents a significant advance in the field of 17 O NMR studies of proteins.