A structural comparison of type c lysozymes based on their hydropathic profiles.

Hydropathic profiles can be considered as an approach to the three-dimensional structure of a protein and so their use for comparison of homologous proteins is proposed, as they provide information on relative structural conservativeness. A simple approach was developed for comparison of hydropathic profiles and applied to 19 lysozymes c of known primary structure. Trees were constructed in order to discover which method yielded the best estimation of the phenotypic differences between the proteins considered, by means of the goodness-of-fit criterion. Iterative methods, such as the Fitch-and-Margoliash and the unweighted-pair-group methods, gave a better fit than did a non-iterative method. When the hydropathic approach is used for comparison of lysozymes c, the enzyme obtained from chachalaca egg-white is placed closer to those from pheasant-like birds than to those of ducks; this result agrees with the morphological resemblance of the chachalaca to pheasant-like birds. Pigeon egg-white and equine milk lysozymes differ greatly in sequence from other lysozymes c and their hydropathic analysis shows important differences with respect to the other homologous enzymes.