Dynamics of saxitoxin binding to saxiphilin c-lobe reveals conformational change.
Thermodynamic parameters (DeltaG, DeltaH, DeltaS, DeltaC(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, DeltaH degrees =-11.7+/-0.8 kcal/mol, and DeltaS degrees =1.17+/-0.07 cal/molK. Analysis of DeltaC(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.
Lewis
Penny
P
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
Fritsch
Ingrid
I
Gawley
Robert E
RE
Henry
Ralph
R
Kight
Alicia
A
Lay
Jackson O
JO
Liyanage
Rohana
R
McLachlin
Jeanne
J
D000818:Animals; D001665:Binding Sites; D013058:Mass Spectrometry; D008968:Molecular Conformation; D011042:Poisons / Q000737:chemistry*; D012530:Saxitoxin / Q000737:chemistry*; D012758:Shellfish; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
D011042:Poisons; D012530:Saxitoxin