Amino-acid-type selective isotope labeling of proteins expressed in Baculovirus-infected insect cells useful for NMR studies.

Culture conditions for successful amino-acid-type selective isotope labeling of proteins expressed in Baculovirus-infected insect cells are described. The method was applied to the selective labeling of the catalytic domain of c-Abl kinase with (15)N-phenylalanine, (15)N-glycine, (15)N-tyrosine or (15)N-valine. For the essential amino acids phenylalanine, tyrosine and valine high (15)N-label incorporation rates of >/=90% and approximately the expected number of resonances in the HSQC spectra were observed, which was not the case for the non-essential amino acid glycine. The method should be applicable to amino-acid-type selective isotope labeling of other recombinant proteins which have not been amenable to NMR analysis.