title: Dynamics of saxitoxin binding to saxiphilin c-lobe reveals conformational change.
abstract: 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Penny
authors.initials: P
authors.lastname: Lewis
authors.forename: Ingrid
authors.initials: I
authors.lastname: Fritsch
authors.forename: Robert E
authors.initials: RE
authors.lastname: Gawley
authors.forename: Ralph
authors.initials: R
authors.lastname: Henry
authors.forename: Alicia
authors.initials: A
authors.lastname: Kight
authors.forename: Jackson O
authors.initials: JO
authors.lastname: Lay
authors.forename: Rohana
authors.initials: R
authors.lastname: Liyanage
authors.forename: Jeanne
authors.initials: J
authors.lastname: McLachlin
mesh_terms: 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
chemical_list: D011042:Poisons; D012530:Saxitoxin