Application of the 'profiles of relationship' method to distantly related proteins.

An analysis is made of the applicability of the recently published 'profiles of relationship' method for establishing evolutionary relatedness among proteins by using the distantly related proinsulin and neurotoxin protein sequences as a test object. The method is based on a simultaneous group analysis of both the frequency of acceptance of mutations and their genetic code interchangeability. Regularities in the patterns of the profiles, which reflect decreased similarity with the passage of time, are established for typical cases of closely related, distantly related and unrelated proteins. This makes it possible to distinguish distantly related from unrelated proteins without extensive statistical randomization procedures. New evidence is stated in favour of a previously suggested definition of interchangeability which does not consider the third base in the codon. The applicability of the profiles of relationship method is examined on the distant relationship between proinsulin and the snake and scorpion neurotoxins which has been established previously by means of conventional approaches.