Article ID Journal Published Year Pages File Type
2065982 Toxicon 2008 10 Pages PDF
Abstract

Thermodynamic parameters (ΔG, ΔH, ΔS, ΔCp) have been determined to evaluate the dynamics of binding of saxitoxin to the c-lobe of saxiphilin. We have developed an improved method to rapidly express and purify recombinant saxiphilin c-lobe, and fully characterized it by mass spectrometry for the first time. Surface plasmon resonance (SPR) was used to characterize the interaction between saxitoxin and immobilized c-lobe. At 298 K, c-lobe binds saxitoxin with KD=1.2 nM, ΔH°=−11.7±0.8 kcal/mol, and ΔS°=1.17±0.07 cal/mol K. Analysis of ΔCp of toxin association at several temperatures suggests that hydrophobic forces contribute to the binding event. Additionally, changes in 8-anilino-1-naphthalene sulfonic acid (ANS) fluorescence upon binding to c-lobe in the presence and absence of saxitoxin support a conformational change in c-lobe upon saxitoxin binding.

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