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Active‐site geometry of proteinase K
Author(s) -
Betzel Christian,
Pal Gour P.,
Struck Mark,
Jany Klaus-Dieter,
Saenger Wolfram
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80307-6
Subject(s) - chemistry , stereochemistry , subtilisin , oxyanion hole , active site , hydrogen bond , oxyanion , antiparallel (mathematics) , residue (chemistry) , covalent bond , endopeptidase , enzyme , catalysis , biochemistry , organic chemistry , physics , quantum mechanics , molecule , magnetic field
Proteinase K (EC 3.4.21.14) from the fungus Tritirachium album Limber is the most active known serine endopeptidase. The sequence of its 275‐residue long polypeptide chain and its three‐dimensional folding show a high degree of homology with the bacterial subtilisin proteases. Using difference Fourier methods, the binding mode of the synthetic carbobenzoxy‐Ala‐Ala‐chloromethyl ketone inhibitor to the active site of proteinase K was determined. In several cycles of restrained least‐squares, the enzyme‐inhibitor complex was refined to a current R = 12% for 9400 X‐ray diffraction data between 2.2 and 5.0 Å resolution. The inhibitor is attached to proteinase K by two covalent bonds; one between the methylene carbon of the inhibitor and Nϵ2 of the catalytic His 68, the other between the ketone carbon atom of the inhibitor and Oγ of the catalytic Ser 221. In addition, two hydrogen bonds donated by the peptide NH of Ser 221 and by the side chain NH 2 of Asn 160 hold the hemiketal O − in the oxyanion hole. The peptide inhibitor is further hydrogen bonded to the proteinase polypeptide chain in a three‐stranded antiparallel pleated sheet.