Quantitative assessment of paraoxon adsorption to amphiphilic β-sheet peptides presenting the catalytic triad of esterases

Avigail Baruch Leshem; Sivan Isaacs; Sachin K Srivastava; Ibrahim Abdulhalim; Ariel Kushmaro; Hanna Rapaport

doi:10.1016/j.jcis.2018.06.065

Quantitative assessment of paraoxon adsorption to amphiphilic β-sheet peptides presenting the catalytic triad of esterases

J Colloid Interface Sci. 2018 Nov 15:530:328-337. doi: 10.1016/j.jcis.2018.06.065. Epub 2018 Jun 23.

Authors

Avigail Baruch Leshem¹, Sivan Isaacs², Sachin K Srivastava², Ibrahim Abdulhalim³, Ariel Kushmaro⁴, Hanna Rapaport⁵

Affiliations

¹ Unit of Environmental Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
² Department of Electro-optic Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
³ Department of Electro-optic Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; School of Materials Science and Engineering, Nanyang Technological University, Singapore; The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
⁴ Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; National Institute for Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
⁵ Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel. Electronic address: hannarap@bgu.ac.il.

PMID: 29982025
DOI: 10.1016/j.jcis.2018.06.065

Abstract

Organophosphate compounds that are used as pesticides affect the nervous system by binding irreversibly to the active site of the enzyme acetylcholine esterase (AChE) and disrupting neuro-signaling nerve cells. In this study we characterized adsorption of paraoxon to a set of designed peptides that present different arrangements of the three amino acids of the AChE catalytic site: histidine, glutamic-acid and serine. The peptides set included two β-strands with no net charge and three β-hairpins that differ in their net charge. Circular dichroism, Thioflavin T assays and TEM images provided only qualitative insights on paraoxon binding to the different peptides. Paraoxon binding to the different peptides was measured with dialysis membrane tubes filled with the peptide solutions and suspended in a reservoir of paraoxon solution. Among all the tested peptides, the single strand peptide, denoted ssESH exhibited at 100 μM in random conformation prefibrillar state, the maximum paraoxon adsorption, with a binding mol ratio of one paraoxon per two peptides and an estimated equilibrium binding constant 5 ∗ 10⁴ M^-1. The three β-hairpin peptides demonstrated that a net negative charge is unfavorable for paraoxon adsorption. Surface enhanced Raman spectroscopy measurements with ssESH enabled the detection of nanomolar adsorbed concentrations of paraoxon.

Keywords: Catalytic triad; Circular dichroism; Organophosphates; Surface enhanced Raman spectroscopy; Thioflavin T; β-hairpin; β-sheet.

MeSH terms

Acetylcholinesterase / chemistry*
Acetylcholinesterase / metabolism
Adsorption
Catalytic Domain / drug effects*
Cholinesterase Inhibitors / pharmacology*
Cholinesterase Inhibitors / toxicity
Humans
Insecticides / pharmacology*
Insecticides / toxicity
Paraoxon / pharmacology*
Paraoxon / toxicity
Peptides / chemistry*
Peptides / metabolism
Protein Conformation, beta-Strand / drug effects
Spectrum Analysis, Raman

Substances

Cholinesterase Inhibitors
Insecticides
Peptides
Acetylcholinesterase
Paraoxon