CHEMICAL-SHIFT HOMOLOGY IN PROTEINS

The degree of chemical shift similarity for homologous proteins has be en determined from a chemical shift database of over 50 proteins repre senting a variety of families and folds, and spanning a wide range of sequence homologies. After sequence alignment, the similarity of the s econdary chemical shifts of C-alpha protons was examined as a function of amino acid sequence identity for 37 pairs of structurally homologo us proteins. A correlation between sequence identity and secondary che mical shift rmsd was observed. Important insights are provided by exam ining the sequence identity of homologous proteins versus percentage o f secondary chemical shifts that fall within 0.1 and 0.3 ppm threshold s. These results begin to establish practical guidelines for the exten t of chemical shift similarity to expect among structurally homologous proteins.