Modification of an Anopheles gambiae odorant binding protein to create an array of chemical sensors for detection of drugs

Khasim Cali,Krishna C Persaud

doi:10.1038/s41598-020-60824-7

Abstract

The binding pockets of odorant binding proteins from Anopheles gambiae (OBP1 and OBP47) were analysed using in silico modelling. The feasibility of creating mutant proteins to achieve a protein array capable of detecting drugs of abuse in solution or in vapour phase was investigated. OBP1 was found to be easily adapted and several mutant proteins were expressed and characterised. AgamOBP1_S82P was found to have high affinities to cannabinol, 3,4-methylenedioxy methamphetamine (MDMA/Ecstasy) and cocaine hydrochloride. When these proteins were immobilised on a quartz crystal microbalance, saturated cocaine hydrochloride vapour could be detected. The sensors were stable over a period of at least 10 months in air. The approach taken allows flexible design of new biosensors based on inherently stable protein scaffolds taking advantage of the tertiary structure of odorant binding proteins.

Highlights

The binding pockets of odorant binding proteins from Anopheles gambiae (OBP1 and OBP47) were analysed using in silico modelling
The X-ray structure (PBD accession number: 2ERB) of Anopheles gambiae OBP1 (AgamOBP1) complexed with polyethylene glycol (PEG) was used as a starting point (Supplementary Fig. S1). This was chosen against other available AgamOBP1- ligand complex structures such as AgamOBP1- DEET (PDB ID: 3N7H), Icaridin (PDB ID: 5EL2), and 6-MH (6-methyl-5-heptene-2-one) (PDB ID: 4FQT) because PEG is a larger molecule compared to the other ligands spanning the whole of the AgamOBP1 monomer through the entire tunnel shaped active site of the protein[29,30,31] (Supplementary Fig. S2)
The Ligand-Protein Contacts (LPC)/Contacts of Structural Units (CSU) (Weizmann, AC) server was used to identify binding pocket residues that interact with the ligands in AgamOBP1, based on the X-ray structure of the protein

Summary

Introduction

The binding pockets of odorant binding proteins from Anopheles gambiae (OBP1 and OBP47) were analysed using in silico modelling. The nasal mucus of non-aquatic vertebrates and the chemosensillar lymph of insect antennae contain large amounts of small soluble odorant-binding proteins (OBPs) that and reversibly bind odour molecules and pheromones In vertebrates these proteins form part of the lipocalin family – low molecular weight proteins characterised by a cage-like structure of beta-sheets that function as carriers of small ligands[4]. Larisika et al immobilised OBP14 from the honeybee on graphene and incorporated it into a field-effect transistor to produce biosensors able to discriminate ligands in a way that was similar to the specificity of the protein when measured in solution[13] These developments are due to the large body of information available on structure and function of OBPs in a variety of species. Eight α-helices are observed in OBP47 rather than the six in classical OBPs such as AgamOBP1

Methods

Results

Conclusion