Biomolecular Fishing for Calixarene Partners by a Chemoproteomic Approach

MS-based chemical-proteomics technology is introduced herein as a third general strategy to study the biomolecular recognition properties of given calixarene derivatives. In particular, we demonstrate that a simply designed calix[4]arene derivative 1 a bearing acetamido groups at the exo rim (pAC), when linked to a solid support, is able to fish out a specific protein (PDI protein) from a crude extract of HeLa cells. Western blot and surface plasmon resonance studies confirmed the direct interaction between PDI and the linker-free pAC derivative 1 b with considerable affinity, and in vitro tests showed its inhibition of PDI chaperone activity. In accordance with the role of PDI in a variety of human cancers, biological tests showed that pAC 1 b was cytotoxic and cytostatic toward CAL-27 and PC-3 cancer cell lines in vitro. Docking studies showed that H bonds and hydrophobic interactions contribute to the stabilization of the PDI/pAC complex.