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Hematopoietic progenitor kinase 1 (HPK1) is an intracellular kinase that plays an important role in modulating tumor immune response and thus is an attractive target for drug discovery. Crystallization of the wild‐type HPK1 kinase domain has been hampered by poor expression in recombinant systems and poor solubility. In this study, yeast surface display was applied to a library of HPK1 kinase‐domain variants in order to select variants with an improved expression level and solubility. The HPK1 variant with the most improved properties contained two mutations, crystallized readily in complex with several small‐molecule inhibitors and provided valuable insight to guide structure‐based drug design. This work exemplifies the benefit of yeast surface display towards engineering crystallizable proteins and thus enabling structure‐based drug discovery. [ABSTRACT FROM AUTHOR]

The Na V 1.7 voltage-gated sodium channel is implicated in human pain perception by genetics. Rare gain of function mutations in Na V 1.7 lead to spontaneous pain in humans whereas loss of function mutations results in congenital insensitivity to pain. Hence, agents that specifically modulate the function of Na V 1.7 have the potential to yield novel therapeutics to treat pain. The complexity of the channel and the challenges to generate recombinant cell lines with high Na V 1.7 expression have led to a surrogate target strategy approach employing chimeras with the bacterial channel Na V Ab. In this report we describe the design, synthesis, purification, and characterization of a chimera containing part of the voltage sensor domain 2 (VSD2) of Na V 1.7. Importantly, this chimera, DII S1-S4, forms functional sodium channels and is potently inhibited by the Na V 1.7 VSD2 targeted peptide toxin ProTx-II. Further, we show by [ 125 I]ProTx-II binding and surface plasmon resonance that the purified DII S1-S4 protein retains high affinity ProTx-II binding in detergent. We employed the purified DII S1-S4 protein to create a scintillation proximity assay suitable for high-throughput screening. The creation of a Na V 1.7-Na V Ab chimera with the VSD2 toxin binding site provides an important tool for the identification of novel Na V 1.7 inhibitors and for structural studies to understand the toxin-channel interaction., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)