Relations between size, secondary structure content and amino acid composition in globular proteins

1. A statistical analysis of the relations between the size, helical, B-strand content and amino acid composition on 27 globular proteins has been undertaken. 2. The helical content was correlated with composition of helix-forming and inversely with that of helix-breaking amino acids, though the degree of correlation was stronger with the latter. 3. The B-strand composition showed little correlation with the composition of either B-sheet favouring or breaking amino acids, however it was strongly correlated with the composition of helix-breaking amino acids and inversely correlated with the helical content. 4. The dependence between these two types of secondary structure was related to the size of the protein since the total number of amino acid residues within these two types of secondary structure was linearly dependent on the total number of amino acids of these globular proteins.