title: S-S bridges of cathepsin B and H from bovine spleen: a basis for cathepsin B model building and possible functional implications for discrimination between exo- and endopeptidase activities among cathepsins B, H and L.
abstract: Bovine spleen cathepsin B contains 7 disulfide bridges. Using different chemical and enzymatic cleavage methods we isolated fragments representing the individual disulfides: Cys14-Cys43, Cys26-Cys71, Cys62-Cys128, Cys63-Cys67, Cys100-Cys132, Cys108-Cys119, and Cys148-Cys252. A similar line of approach was applied to determine the S-S bridges of bovine spleen cathepsin H: Cys23-Cys66, Cys57-Cys99, Cys157-Cys207, and Cys212-Cys5A, where Cys5A is located in the propart portion of the procathepsin H chain. On the basis of the knowledge of the S-S bridges of cathepsin B a novel sequence alignment of papain and cathepsin B has been proposed. This enabled us to construct a reasonable 3D-model of cathepsin B and propose the region (a 18 residue insertion between Glu89 and Gly90 of papain) responsible for the carboxypeptidase activity of cathepsin B functioning as a "closure". A similar approach was applied to explain the aminopeptidase activity of cathepsin H. A general model of steric regulation of accessibility of the preformed "endopeptidase-like" binding cleft by distant parts of the polypeptide chain of the proteinases discussed is proposed as a factor determining the mode of binding and thus cleavage of polypeptide substrates.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, Prague, CSFR.
authors.forename: M
authors.initials: M
authors.lastname: Baudys
authors.forename: B
authors.initials: B
authors.lastname: Meloun
authors.forename: T
authors.initials: T
authors.lastname: Gan-Erdene
authors.forename: M
authors.initials: M
authors.lastname: Fusek
authors.forename: M
authors.initials: M
authors.lastname: Mares
authors.forename: V
authors.initials: V
authors.lastname: Kostka
authors.forename: J
authors.initials: J
authors.lastname: Pohl
authors.forename: C C
authors.initials: CC
authors.lastname: Blake
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002401:Cathepsin B / Q000737:chemistry*; D056655:Cathepsin H; D056668:Cathepsin L; D002403:Cathepsins / Q000737:chemistry*; D002417:Cattle; D003545:Cysteine / Q000737:chemistry; D003546:Cysteine Endopeptidases; D004220:Disulfides / Q000737:chemistry; D010450:Endopeptidases / Q000737:chemistry; D020689:Exopeptidases; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D013154:Spleen / Q000201:enzymology
chemical_list: D004220:Disulfides; D002403:Cathepsins; D010450:Endopeptidases; D020689:Exopeptidases; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056668:Cathepsin L; D056655:Cathepsin H; D003545:Cysteine