[X-ray study of chymosin. I. Molecular replacement at a 3 angstroms resolution].

The determination of the three dimensional structure of chymosin at 3 A resolution by molecular replacement method is described. The rotation functions for various aspartic proteases were calculated and combined results were used for the refinement of orientational parameters of chymosin molecules in the unit cell. The interpretation of Crowther-Blow translation function map with packing consideration enable to place correctly the molecules in the chymosin unit cell. Several difference Fourier syntheses for chymosin were calculated and differences between pepsin and chymosin structures were detected.