8d6s
Rana catesbeiana saxiphilin mutant - Y558A:STX (co-crystal)
Structural highlights
FunctionSAX_AQUCT Binds specifically to the neurotoxin saxitoxin. Its physiological role may be to transport or sequester an endogenous organic molecule other than Fe(3+). It may participate in a detoxification mechanism for neutralizing a microbial toxin. Publication Abstract from PubMedAmerican bullfrog (Rana castesbeiana) saxiphilin (RcSxph) is a high-affinity "toxin sponge" protein thought to prevent intoxication by saxitoxin (STX), a lethal bis-guanidinium neurotoxin that causes paralytic shellfish poisoning (PSP) by blocking voltage-gated sodium channels (Na(V)s). How specific RcSxph interactions contribute to STX binding has not been defined and whether other organisms have similar proteins is unclear. Here, we use mutagenesis, ligand binding, and structural studies to define the energetic basis of Sxph:STX recognition. The resultant STX "recognition code" enabled engineering of RcSxph to improve its ability to rescue Na(V)s from STX and facilitated discovery of 10 new frog and toad Sxphs. Definition of the STX binding code and Sxph family expansion among diverse anurans separated by approximately 140 My of evolution provides a molecular basis for understanding the roles of toxin sponge proteins in toxin resistance and for developing novel proteins to sense or neutralize STX and related PSP toxins. Definition of a saxitoxin (STX) binding code enables discovery and characterization of the anuran saxiphilin family.,Chen Z, Zakrzewska S, Hajare HS, Alvarez-Buylla A, Abderemane-Ali F, Bogan M, Ramirez D, O'Connell LA, Du Bois J, Minor DL Jr Proc Natl Acad Sci U S A. 2022 Nov;119(44):e2210114119. doi: , 10.1073/pnas.2210114119. Epub 2022 Oct 24. PMID:36279441[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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