Heparin Blocks the Inhibition of Tissue Kallikrein 1 by Kallistatin through Electrostatic Repulsion

Biomolecules

RobinW. Carrell¹  Lina Ma²  Zhenquan Wei²  Zimei Shu²  Jiawei Wu²  Ying Zheng²  Aiwu Zhou²  Yinbiao Sun³ 

[1] Department of Haematology, University of Cambridge, Cambridge CB2 0XY, UK;Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China;Randall Division of Cell & Molecular Biophysics, Faculty of Life Sciences & Medicine, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 1UL, UK;

关键词: serpins;    tissue kallikrein;    heparin;    serine protease;    electrostatic repulsion;   

DOI  :  10.3390/biom10060828

来源: DOAJ

【 摘 要 】

Kallistatin, also known as SERPINA4, has been implicated in the regulation of blood pressure and angiogenesis, due to its specific inhibition of tissue kallikrein 1 (KLK1) and/or by its heparin binding ability. The binding of heparin on kallistatin has been shown to block the inhibition of KLK1 by kallistatin but the detailed molecular mechanism underlying this blockade is unclear. Here we solved the crystal structures of human kallistatin and its complex with heparin at 1.9 and 1.8 Å resolution, respectively. The structures show that kallistatin has a conserved serpin fold and undergoes typical stressed-to-relaxed conformational changes upon reactive loop cleavage. Structural analysis and mutagenesis studies show that the heparin binding site of kallistatin is located on a surface with positive electrostatic potential near a unique protruded 3¹⁰ helix between helix H and strand 2 of β-sheet C. Heparin binding on this site would prevent KLK1 from docking onto kallistatin due to the electrostatic repulsion between heparin and the negatively charged surface of KLK1, thus blocking the inhibition of KLK1 by kallistatin. Replacement of the acidic exosite 1 residues of KLK1 with basic amino acids as in thrombin resulted in accelerated inhibition. Taken together, these data indicate that heparin controls the specificity of kallistatin, such that kinin generation by KLK1 within the microcirculation will be locally protected by the binding of kallistatin to the heparin-like glycosaminoglycans of the endothelium.

【 授权许可】

Unknown