2019/06/01 by Tien-Jui Yen, Marco Lolicato, Rhiannon Thomas‐Tran +2 · 2 citations
Environmental Science · Biochemistry, Genetics and Molecular Biology · #Marine Toxins and Detection Methods #Ion channel regulation and function #Nicotinic Acetylcholine Receptors Study
paper · pdf · doi:10.1126/sciadv.aax2650
openalex publication_date 2019/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Dinoflagelates and cyanobacteria produce saxitoxin (STX), a lethal bis-guanidinium neurotoxin causing paralytic shellfish poisoning. A number of metazoans have soluble STX-binding proteins that may prevent STX intoxication. However, their STX molecular recognition mechanisms remain unknown. Here, we present structures of saxiphilin (Sxph), a bullfrog high-affinity STX-binding protein, alone and bound to STX. The structures reveal a novel high-affinity STX-binding site built from a "proto-pocket" on a transferrin scaffold that also bears thyroglobulin domain protease inhibitor repeats. Comparison of Sxph and voltage-gated sodium channel STX-binding sites reveals a convergent toxin recognition strategy comprising a largely rigid binding site where acidic side chains and a cation-π interaction engage STX. These studies reveal molecular rules for STX recognition, outline how a toxin-binding site can be built on a naïve scaffold, and open a path to developing protein sensors for environmental STX monitoring and new biologics for STX intoxication mitigation.