Inhibition of soluble recombinant furin by human proteinase inhibitor 8.
Furin is a ubiquitous prototypical mammalian kexin/subtilisin-like endoproteinase that is involved in the proteolytic processing of a variety of proteins in the exocytic and endocytic pathways, with cleavage occurring at the C terminus of the minimal consensus furin recognition sequence Arg-Xaa-Xaa-Arg. In this study, human proteinase inhibitor 8 (PI8), a widely expressed 45-kDa ovalbumin-type serpin that contains two sequences homologous to the minimal sequence for recognition by furin in its reactive site loop, was tested for its ability to inhibit a recombinant soluble form of human furin. PI8 formed an SDS-stable complex with furin and inhibited its amidolytic activity via a two-step mechanism with a kappa assoc of 6.5 x 10(5) M-1 S-1 and an overall Ki of 53.8 pM. Thus, PI8 inhibits furin in a rapid, tight binding manner that is characteristic of physiological serpin-proteinase interactions. PI8 is not only the first human ovalbumin-type serpin to demonstrate inhibitory activity toward furin, but it is also the first significant inhibitor of furin identified that is not a serpin reactive site loop mutant, either naturally occurring or engineered.
Dahlen
J R
JR
Department of Pathology, University of New Mexico School of Medicine, Albuquerque 87131, USA.
Jean
F
F
Thomas
G
G
Foster
D C
DC
Kisiel
W
W
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D045683:Furin; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011485:Protein Binding; D011817:Rabbits; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D015843:Serpins / Q000494:pharmacology*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D012995:Solubility; D013381:Subtilisins / Q000037:antagonists & inhibitors*; D013501:Surface-Active Agents / Q000494:pharmacology
D011994:Recombinant Proteins; C108403:SERPINB8 protein, human; D015843:Serpins; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D013381:Subtilisins; D045683:Furin