A simple method for the calculation of low energy packings of alpha-helices--a threshold approximation. I. The use of the method to estimate the effects of amino acid substitutions, deletions and insertions in globins

Single amino acid substitutions producing instability of globular proteins. Calculation of their frequencies in the entire mutational spectra of the alpha- and beta-subunits of human hemoglobin

The frequencies of substitutions resulting in protein instability were calculated by a method estimating changes in stability produced by amino acid substitutions. The method takes into account the accessibility of an amino acid position to a solvent and changes in the specificity of amino acid interactions. When tested on human mutant hemoglobins, the method yielded predictions with a preciseness of 80%. The consideration of the evolutionary homologous proteins in the analysis allowed us to estimate the evolutionary constraints imposed on stability of their spatial structure. With these limitations, approximately 50% of amino acid substitutions in the entire mutational spectra of the alpha- and beta-subunits of human hemoglobin were found to damage the spatial structure of the globular proteins.