Three-dimensional Structure of Goose-type Lysozyme from the Egg White of the Australian Black Swan, Cygnus atratus

Abstract

The egg white of C. atratus contains two forms of lysozyme, a 'chick-type' which is similar to that found in the egg white of the domestic hen, and a 'goose-type' similar to that found in the egg white of the Embden goose. The molecular structure of the goose-type lysozyme has been determined at a resolution of a 2' 8 A by X-ray crystallographic analysis. The structure consists of two domains linked by a long stretch of a-helix. In all, there are seven helical segments in the structure. While there is no amino acid sequence homology with either hen egg-white or bacteriophage T4lysozymes, there are portions of the structure where the folding of the main chain is similar to that found in portions of either hen egg-white lysozyme or T4 lysozyme or both. In particular, there is a consistency of structure in the arrangement of acid groups in the catalytic site.