Mutation severity

Purpose of this page

This web page is designed to give a hint to the severity of an amino acid substitution. The rate at which amino acids are seen to mutate to other residues in homologous proteins as been extensively studied to create substitution matrixes for sequence alignment. These score the likelihood that an amino acid in a protein will change to another during evolution.

For example tryptophan is highly conserved and rarely changes to any other amino acid, where as isoleucine, leucine and valine are interchangeable. Therefore the score for tryptophan > tryptophan (no change) is 17 compared to tryptophan > glycine is -7. However, leucine > leucine is only 6 and leucine > valine or leucine to isoleucine is 2.

It must be remembered that the score as a direction, so tryptophan > glycine is 17 > -7, but glycine > tryptophan is 5 to -7. Also some residues have an important function and so may be important changes but have a low score, for example E > D as a score of 1, but in long chain alcohol dehydrogenases, glutamic acid binds the active site zinc atom, a function which aspartic acid can not replicate in the same protein.

A Windows program that duplicates this page can be downloaded here.

Instructions

Select the wildtype and mutant amino acid residues from the two lists and press 'Submit'.