A novel methodology for sequence-specific resonance assignments in proteins
, using amino acid selective 'unlabelling' is presented. The strategy is ba
sed on selective unlabelling of amino acid residues in uniformly or fractio
nally C-13 or/and N-15 labeled proteins, which simplify the multi-dimension
al heteronuclear NMR spectra. This aids in sequence-specific resonance assi
gnments of both backbone and side-chain nuclei, The methodology has been de
monstrated by unlabelling Lys residues in a 15 kDa calcium-binding protein
from Entamoeba histolytica (Eh-CaBP).