Dynamics of saxitoxin binding to saxiphilin c-lobe reveals conformational change
by Lewis, Penny; Fritsch, Ingrid; Gawley, Robert E.; Henry, Ralph; Kight, Alicia; Lay, Jackson O.; Liyanage, Rohana; McLachlin, Jeanne
Thermodynamic parameters (Delta G, Delta H, Delta S, Delta C-p) 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 K-D = 1.2 nM, Delta H degrees = -11.7 +/- 0.8 kcal/mol, and Delta S degrees = 1.17 +/- 0.07 cal/mol K. Analysis of Delta C-p 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.
- Journal
- Toxicon
- Volume
- 51
- Issue
- 2
- Year
- 2008
- Start Page
- 208-217
- URL
- https://dx.doi.org/10.1016/j.toxicon.2007.09.012
- ISBN/ISSN
- 1879-3150; 0041-0101
- DOI
- 10.1016/j.toxicon.2007.09.012