Crystal structure of Turkey egg-white lysozyme: Results of the molecular replacement method at 5 Å resolution

Abstract

Turkey egg-white lysozyme differs from hen egg-white lysozyme in its primary structure in 7 of the 129 residues. We have determined the rotational and translational parameters relating the known co-ordinates of hen egg-white lysozyme molecule to the turkey lysozyme. The rotational parameters were determined using the rotation function, the translational parameters were determined by placing the properly rotated molecule systematically at all positions within the unit cell and searching for those positions producing few intermolecular contacts between the α-carbon atoms of one molecule and all its neighbors. These parameters were refined by minimizing the conventional R factor between observed and calculated structure amplitudes. The final rotational and translational parameters give an R value of 46.7% for reflections with d spacings between 6 Å and 12 Å and have 7 intermolecular contacts closer than 5 Å between the a carbon atoms of one molecule and all its neighbors. An electron density map has been calculated at 5 Å resolution; the packing of the molecules in this form appears to present the entire length of the active cleft in the vicinity of the crystallographic 6-fold axis and does not appear to be blocked by neighboring molecules.