Comparison of the X-ray structure of baboon alpha-lactalbumin and the tertiary predicted computer models of human alpha-lactalbumin.

The previously predicted structures of human alpha-lactalbumin by homology with hen egg white lysozyme by an automatic method, after the alignment stage, are compared to the X-ray determined structure of baboon alpha-lactalbumin. The root mean square by rotation method (RMSR) deviations for 122 C-alpha atoms between the two models and the X-ray structure are 2.0 A and 2.3 A. The RMSR deviations for all atoms, except for differences in human and baboon sequences, are 2.8 A and 3.1 A. If the flexible C-terminus (residues 112-122) are removed then these RMSR deviations are reduced to 2.4 A and 2.3 A respectively. These results are consistent with the fact that the RMSR deviation between the human and baboon X-ray structures increases from residue 112 onwards and is conformationally flexible.