The three-dimensional structure of the lysozyme produced by Streptomyces erythraeus

Streptomyces erythraeus lysozyme is different in its amino acid composition, primary structure, and specificity from all other mammalian lysozymes. The structure of the crystalline enzyme has been determined by x-ray diffraction analysis to a resolution of 2.9 A using multiple isomorphous replacement. The primary structure of the enzyme is only partially known and therefore the electron density map has been fitted with all the atoms of the main polypeptide chain and some atoms of the side chain. The enzyme consists of three different domains, and about 18% of the structure has helical conformation. A comparison of the tertiary structure of the bacterial lysozyme with either the mammalian or phage lysozyme does not show any obvious similarities.