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Open Access Highly Accessed Research article

Structure of catalytic domain of Matriptase in complex with Sunflower trypsin inhibitor-1

Cai Yuan1, Liqing Chen2, Edward J Meehan2, Norelle Daly3, David J Craik3, Mingdong Huang1* and Jacky C Ngo4*

Author Affiliations

1 State Key Lab of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China

2 Laboratory for Structural Biology, Department of Chemistry, University of Alabama in Huntsville, Huntsville, AL 35899, USA

3 University of Queensland, Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, Brisbane, Queensland 4072, Australia

4 The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China

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BMC Structural Biology 2011, 11:30  doi:10.1186/1472-6807-11-30

Published: 22 June 2011



Matriptase is a type II transmembrane serine protease that is found on the surfaces of epithelial cells and certain cancer cells. Matriptase has been implicated in the degradation of certain extracellular matrix components as well as the activation of various cellular proteins and proteases, including hepatocyte growth factor and urokinase. Sunflower trypsin inhibitor-1 (SFTI-1), a cyclic peptide inhibitor originally isolated from sunflower seeds, exhibits potent inhibitory activity toward matriptase.


We have engineered and produced recombinant proteins of the matriptase protease domain, and have determined the crystal structures of the protease:SFTI-1 complex at 2.0 Å as well as the protease:benzamidine complex at 1.2 Å. These structures elaborate the structural basis of substrate selectivity of matriptase, and show that the matriptase S1 substrate specificity pocket is larger enough to allow movement of benzamidine inside the S1 pocket. Our study also reveals that SFTI-1 binds to matriptase in a way similar to its binding to trypsin despite the significantly different isoelectric points of the two proteins (5.6 vs. 8.2).


This work helps to define the structural basis of substrate specificity of matriptase and the interactions between the inhibitor and protease. The complex structure also provides a structural template for designing new SFTI-1 derivatives with better potency and selectivity against matriptase and other proteases.