Identification of bovine stefin A, a novel protein inhibitor of cysteine proteinases.
For the first time, three different stefins, A, B and C, have been isolated from a single species. The complete amino acid sequence of bovine stefin A was determined. The inhibitor, with a calculated M(r) of 11,123, consists of 98 amino acid residues. Although it exhibits considerable similarity to human and rat stefin A, some significant differences in inhibition kinetics were found. Bovine stefin A bound tightly and rapidly to cathepsin L (kass = 9.6 x 10(6) M-1.s-1, Ki = 29 pM). The binding to cathepsin H was also rapid (kass = 2.1 x 10(6) M-1.s-1), but weaker (Ki = 0.4 nM) due to a higher dissociation rate constant. In contrast, the binding to cathepsin B was much slower (kass = 1.4 x 10(5) M-1.s-1), but still tight (Ki = 1.9 nM).
Turk
B
B
Department of Biochemistry and Molecular Biology, J. Stefan Institute, Ljubljana, Slovenia.
Ritonja
A
A
Björk
I
I
Stoka
V
V
Dolenc
I
I
Turk
V
V
D000595:Amino Acid Sequence; D000818:Animals; D002403:Cathepsins / Q000037:antagonists & inhibitors; D002417:Cattle; D055312:Cystatin A; D015891:Cystatins / Q000302:isolation & purification*; D015853:Cysteine Proteinase Inhibitors / Q000302:isolation & purification*; D007700:Kinetics; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012867:Skin / Q000201:enzymology
D055312:Cystatin A; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; C026407:CSTA protein, human; D002403:Cathepsins