The relation between amino acid sequence and protein conformation

From studies of the amino acid sequence and conformation of myoglobin, human α- and β-haemoglobins and lysozyme, the following conclusions have been drawn: (a) that aspartic acid, glutamic acid and threonine occur preferentially at the N-terminal end of a helical segment, while lysine, arginine and histidine occur preferentially at the C-terminal end; (b) that alanine, valine and leucine tend to favour an α-helical conformation whereas asparagine, aspartic acid and phenylalanine have a “helix-breaking” effect; (c) that participation of hydrophobic amino acids in an α-helix is to some extent a function of side-chain size.