AN EFFICIENT NMR APPROACH FOR OBTAINING SEQUENCE-SPECIFIC RESONANCE ASSIGNMENTS OF LARGER PROTEINS BASED ON MULTIPLE ISOTOPIC LABELING

By simultaneously incorporating in a protein 13C-carbonyl- and 15N-labeled amino acids with different levels of enrichment, characteristic asymmetric doublet-like patterns are observed for 15N nuclei that are directly adjacent to the 13C1-labeled residues, providing unambiguous identification of a large number of unique dipeptide fragments of the protein. Additional assignments and qualitative structural information can be obtained from such a selectively labeled protein by recording multiple bond correlation spectra. The procedure is demonstrated for the protein calmodulin, complexed with calcium. © 1990.