Primitive haemoglobin.

The sequences of Petromyzon and Aplysia globins are compared with the postulated vertebrate and mollusc-vertebrate ancestors to see if differences exist in the rates of evolution of different types of residue positions. Between the mollusc-vertebrate ancestor and Aplysia globin there is no very striking pattern of changes except that the interior positions are relatively conserved. In the evolution of Petromyzon haemoglobin, the alpha 1 beta 2 contact area is relatively conserved. The homopolymeric binding of lamprey Hb seems to be a primitive function.