A CRITICAL-EVALUATION OF THE PREDICTED AND X-RAY STRUCTURES OF ALPHA-LACTALBUMIN

The rapidly increasing availability of protein amino-acid sequences, many of which have been determined from the corresponding gene sequences, has intensified interest in the prediction of related protein structures when the three-dimensional structure of another member of the family is known. The study of bovine alpha-Lactalbumin provides a classic example in which the three-dimensional structure was predicted, first by Browne et al. (1969) and later by Warme et al. (1974), from the three-dimensional structure of hen-egg-white lysozyme (Blake et al., 1965), taking into account the striking relationship between the amino acid sequences of the two proteins. A comprehensive comparison of these models with the structure of baboon-alpha-Lactalbumin derived from X-ray crystallography (Acharya et al., 1989) is presented. The models mostly compare well with the experimentally determined structure except in the flexible C-terminal region of the molecule (rms deviation on C-alpha-S of residues 1-95, 1.1 angstrom).