Amino acid distribution in protein secondary structures.

The compositional distribution of the twenty amino acids was examined for particular positions within secondary structures (alpha-helices, beta-strands, and turns) taken from a 44-protein sample. Correlation coefficients calculated between positional composition of the amino acids and various of their physico-chemical characteristics indicated considerable asymmetry in the properties of the residues comprising regions within and adjacent to secondary structures, modes of helix formation, physical parameters most sensitive to the buriedness of residues in beta-strands, and possible improvements in the accuracy of secondary structure prediction methodologies.