A novel super-secondary structure of proteins and the relation between the structure and the amino acid sequence

A novel protein super-secondary structure which is referred to as an alpha alpha-corner is considered. The alpha alpha-corner is formed by two consecutive alpha-helices packed approximately crosswise and connected by two or more peptide units. It is shown that the amino acid sequences coding for the alpha alpha-corners have a strictly definite order of hydrophobic, hydrophilic and glycine residues. A hypothesis is suggested that the alpha alpha-corner can be an embryo of protein folding.