Crystal Structure of a Two-domain Fragment of Hepatocyte Growth Factor Activator Inhibitor-1: FUNCTIONAL INTERACTIONS BETWEEN THE KUNITZ-TYPE INHIBITOR DOMAIN-1 AND THE NEIGHBORING POLYCYSTIC KIDNEY DISEASE-LIKE DOMAIN.

Abstract

Hepatocyte growth factor activator inhibitor-1 (HAI-1) is a type I transmembrane protein and inhibitor of several serine proteases, including hepatocyte growth factor activator and matriptase. The protein is essential for development as knock-out mice die in utero due to placental defects caused by misregulated extracellular proteolysis. HAI-1 contains two Kunitz-type inhibitor domains (Kunitz), which are generally thought of as a functionally self-contained protease inhibitor unit. This is not the case for HAI-1, where our results reveal how interdomain interactions have evolved to stimulate the inhibitory activity of an integrated Kunitz. Here we present an x-ray crystal structure of an HAI-1 fragment covering the internal domain and Kunitz-1. The structure reveals not only that the previously uncharacterized internal domain is a member of the polycystic kidney disease domain family but also how the two domains engage in interdomain interactions. Supported by solution small angle x-ray scattering and a combination of site-directed mutagenesis and functional assays, we show that interdomain interactions not only stabilize the fold of the internal domain but also stimulate the inhibitory activity of Kunitz-1. By completing our structural characterization of the previously unknown N-terminal region of HAI-1, we provide new insight into the interplay between tertiary structure and the inhibitory activity of a multidomain protease inhibitor. We propose a previously unseen mechanism by which the association of an auxiliary domain stimulates the inhibitory activity of a Kunitz-type inhibitor (i.e. the first structure of an intramolecular interaction between a Kunitz and another domain).

• Authors: Zebin Hong, Laura De Meulemeester, Annemarie Jacobi, Jan Skov Pedersen, J Preben Morth, Peter A Andreasen, Jan K Jensen
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 291 Issue 27 Pg. 14340-14355 (Jul 01 2016) ISSN: 1083-351X [Electronic] United States
• PMID: 27189939 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Membrane Glycoproteins
• Proteinase Inhibitory Proteins, Secretory
• Recombinant Proteins
• Spint1 protein, mouse

Topics

• Amino Acid Sequence
• Animals
• Crystallography, X-Ray
• Membrane Glycoproteins (chemistry, metabolism)
• Mice
• Mice, Knockout
• Models, Molecular
• Molecular Sequence Data
• Polycystic Kidney Diseases (metabolism)
• Protein Binding
• Protein Conformation
• Proteinase Inhibitory Proteins, Secretory
• Recombinant Proteins (chemistry, metabolism)
• Scattering, Small Angle
• Sequence Homology, Amino Acid
• Surface Plasmon Resonance