A preliminary neutron crystallographic study of proteinase K at pD 6.5

A preliminary neutron crystallographic study of the proteolytic enzyme proteinase K is presented. Large hydrogenated crystals were prepared in deuterated crystallization buffer using the vapor-diffusion method. Data were collected to a resolution of 2.3 Å on the LADI-III diffractometer at the Institut Laue-Langevin (ILL) in 2.5 d. The results demonstrate the feasibility of a full neutron crystallographic analysis of this structure with the aim of providing relevant information on the location of H atoms, particularly at the active site. This information will contribute to further understanding of the molecular mechanisms underlying the catalytic activity of proteinase K and to an enriched understanding of the subtilisin clan of serine proteases.