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X‐ray and model‐building studies on the specificity of the active site of proteinase K
Author(s) -
Betzel C.,
Bellemann M.,
Pal G. P.,
Bajorath J.,
Saenger W.,
Wilson K. S.
Publication year - 1988
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340040302
Subject(s) - subtilisin , active site , stereochemistry , antiparallel (mathematics) , chemistry , endopeptidase , phenylalanine , serine , enzyme , crystallography , biochemistry , amino acid , physics , quantum mechanics , magnetic field
Proteinase K, the extracellular serine endopeptidase (E.C. 3.4.21.14) from the fungus Tritirachium album limber , is homologous to the bacterial subtilisin proteases. The binding geometry of the synthetic inhibitor carbobenzoxy‐Ala‐Phechloromethyl Ketone to the active site of proteinase K was the first determined from a Fourier synthesis based on synchrotron X‐ray diffraction data between 1.8 Å and 5.0 Å resolution. The protein inhibitor complexes was refined by restrained least‐squares minimization with the data between 10.0 and 1.8 Å. The final R factor was 19.1% and the model contained 2,018 protein atoms, 28 inhibitors atoms, 125 water molecules, and two Ca 2+ ions. The peptides portion of the inhibitor is bound to the active center of proteinase K by means of a three‐stranded antiparallel pleated sheet, with the side chain of the phenylalanine located in the P1 site. Model building studies, with lysine replacing phenylalanine in the inhibitor, explain the relatively unspecific catalytic activity of the enzyme.