Author/Editor		Jerala, Roman; Kroon-Žitko, Louisa; Popovič, Tatjana; Turk, Vito
Title		Elongation on the amino-terminal part of stefin B decreases inhibition of cathepsin H
Type		članek
Source		Eur J Biochem
Vol. and No.		Letnik 224
Publication year		1994
Volume		str. 797-802
Language		eng
Abstract		Two mutants of the cysteine proteinase inhibitor, stefin B, were prepared by ligating the aminoterminal region from cystatin C and kininogen, members of two other families of cystatin superfamily. The mutant proteins were expressed in Escherichia coli and purified to homogeneity. Inhibition and kinetic constants were determined for authentic and mutated stefins against the four different cysteine proteinases, papain and human cathepsins B, L and H. Inhibition of both amino-terminal elongated stefin B mutants was decreased particularly for cathepsin H. A model of the tertiary structure of cathepsin H and its complex with stefin B was constructed. The framework for the model of cathepsin H consisted of structurally conserved regions from tertiary structures of three cysteine proteinases. Variable regions were selected from fragments of other proteins from the protein data base. We suggest est that reduced binding of stefins with elongated amino termini is caused by the mini chain of cathepsin H which is probably in close proximity to the amino termini in the complexes. This mini chain is bridged to Cys2l4 and has already been proposed to be responsible for the aminopeptidase activity of cathepsin H. We conclude that the amino-terminal region of stefin B plays an important role in determining the strength of inhibition of cathepsin H.
Descriptors		ESCHERICHIA COLI CYSTATINS CATHEPSINS MUTAGENESIS, SITE-DIRECTED KININOGENS PEPTIDE CHAIN ELONGATION PAPAIN PROTEIN STRUCTURE, TERTIARY MODELS, CHEMICAL