title: Comprehensive study of the interaction between a potential antiprion cationic porphyrin and human prion protein at different pH by using multiple spectroscopic methods.
abstract: Cationic porphyrins are potential antiprion drugs; however, the action mechanisms remain poorly understood. Herein, the interaction between a cationic porphyrin and recombinant human prion protein (rPrP(C)) was comprehensively studied by using surface plasmon resonance (SPR), fluorescence, resonance light scattering (RLS), and circular dichroism (CD) spectroscopy. The experimental results showed that the interaction between the cationic porphyrin and rPrP(C) was pH dependent. The equilibrium association constants obtained from SPR spectroscopy were 4.12 × 10(3) M(-1) at pH 4.0, 1.74 × 10(5) M(-1) at pH 6.0, and 5.98 × 10(5) M(-1) at pH 7.0. The binding constants at 298 K obtained from the fluorescence quenching method were 7.286 × 10(4) M(-1) at pH 4.0 and 1.457 × 10(5) M(-1) at pH 6.0. The thermodynamic parameters such as enthalpy change, entropy change, and free energy change were calculated, and the results indicated hydrogen bonds and van der Waals interactions played a major role in the binding reaction. The RLS experiment was performed to study the influence of porphyrin on the rPrP(C) aggregation at different pH values. The CD experiments were conducted to investigate the effects of porphyrin on the secondary structure and thermal stability of rPrP(C). Finally, the comparison of SPR measurement and fluorescence quenching measurement was discussed.
authors.affiliation: State Key Laboratory of Virology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Chang-Qing
authors.initials: CQ
authors.lastname: Xiao
authors.forename: Bo-Ya
authors.initials: BY
authors.lastname: Feng
authors.forename: Yu-Su
authors.initials: YS
authors.lastname: Ge
authors.forename: Xiao-Yang
authors.initials: XY
authors.lastname: Fan
authors.forename: Feng-Lei
authors.initials: FL
authors.lastname: Jiang
authors.forename: Gengfu
authors.initials: G
authors.lastname: Xiao
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
mesh_terms: D001665:Binding Sites; D002412:Cations / Q000378:metabolism / Q000494:pharmacology; D002942:Circular Dichroism; D006801:Humans; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008027:Light; D011166:Porphyrins / Q000378:metabolism / Q000494:pharmacology*; D018621:PrPC Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D055550:Protein Stability / Q000187:drug effects; D017433:Protein Structure, Secondary / Q000187:drug effects; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
chemical_list: D002412:Cations; D011166:Porphyrins; D018621:PrPC Proteins; D011994:Recombinant Proteins