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==Combinatorial Engineering of Proteolytically Resistant APPI Variants that Selectively Inhibit Human Kallikrein 6 for Cancer Therapy==
<StructureSection load='5nx3' size='340' side='right'caption='[[5nx3]], [[Resolution|resolution]] 2.30&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5nx3]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5NX3 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5NX3 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.296&#8491;</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=5nx3 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5nx3 OCA], [https://pdbe.org/5nx3 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5nx3 RCSB], [https://www.ebi.ac.uk/pdbsum/5nx3 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5nx3 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/KLK6_HUMAN KLK6_HUMAN] Serine protease which exhibits a preference for Arg over Lys in the substrate P1 position and for Ser or Pro in the P2 position. Shows activity against amyloid precursor protein, myelin basic protein, gelatin, casein and extracellular matrix proteins such as fibronectin, laminin, vitronectin and collagen. Degrades alpha-synuclein and prevents its polymerization, indicating that it may be involved in the pathogenesis of Parkinson disease and other synucleinopathies. May be involved in regulation of axon outgrowth following spinal cord injury. Tumor cells treated with a neutralizing KLK6 antibody migrate less than control cells, suggesting a role in invasion and metastasis.<ref>PMID:12878203</ref> <ref>PMID:12928483</ref> <ref>PMID:15557757</ref> <ref>PMID:16987227</ref> <ref>PMID:16321973</ref> <ref>PMID:11983703</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Human tissue kallikrein (KLK) proteases are hormone-like signaling molecules with important functions in cancer pathophysiology. KLK-related peptidase 6 (KLK6), specifically, is highly up-regulated in several types of cancer, where its increased activity promotes cancer invasion and metastasis. This characteristic suggests KLK6 as an attractive target for therapeutic interventions. However, inhibitors that specifically target KLK6 have not yet been reported, possibly because KLK6 shares a high sequence homology and structural similarity with other serine proteases and resists inhibition by many polypeptide inhibitors. Here, we present an innovative combinatorial approach to engineering KLK6 inhibitors via flow cytometry-based screening of a yeast-displayed mutant library of the human amyloid precursor protein Kunitz protease inhibitor domain (APPI), an inhibitor of other serine proteases, such as anionic and cationic trypsins. On the basis of this screening, we generated APPIM17L,I18F,S19F,F34V (APPI-4M), an APPI variant with a KLK6 inhibition constant (Ki ) of 160 pm and a turnover time of 10 days. To the best of our knowledge, APPI-4M is the most potent KLK6 inhibitor reported to date, displaying 146-fold improved affinity and 13-fold improved proteolytic stability compared with WT APPI (APPIWT). We further demonstrate that APPI-4M acts as a functional inhibitor in a cell-based model of KLK6-dependent breast cancer invasion. Finally, the crystal structures of the APPIWT/KLK6 and APPI-4M/KLK6 complexes revealed the structural and mechanistic bases for the improved KLK6 binding and proteolytic resistance of APPI-4M. We anticipate that APPI-4M will have substantial translational potential as both imaging agent and therapeutic.

A potent, proteolysis-resistant inhibitor of kallikrein-related peptidase 6 (KLK6) for cancer therapy, developed by combinatorial engineering.,Sananes A, Cohen I, Shahar A, Hockla A, De Vita E, Miller AK, Radisky ES, Papo N J Biol Chem. 2018 Aug 17;293(33):12663-12680. doi: 10.1074/jbc.RA117.000871. Epub, 2018 Jun 22. PMID:29934309<ref>PMID:29934309</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5nx3" style="background-color:#fffaf0;"></div>

==See Also==
*[[Kallikrein 3D structures|Kallikrein 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Papo N]]
[[Category: Radisky ES]]
[[Category: Sananes A]]
[[Category: Shahar A]]