In Silico Site-Directed Mutagenesis of the Anopheles gambiae Odorant Binding Protein 20

Abstract

The Anopheles gambiae is a highly anthropophilic mosquito which is the leading vector for malaria. This disease has affected more than 500 million people worldwide. The Anopheles gambiae targets its hosts through the odors of the human skin and sweat where odorant molecules radiate. These odors elicit specific responses from the insect through the odorant – binding proteins (OBP). Recently, a specific type of OBP has been characterized which is known as the Anopheles gambiae odorant – binding protein 20 (AgamOBP20). This OBP is highly expressed in the female mosquito antennae during the peak of its host – seeking behavior and thus may play a role in olfactory perception. The binding site of the AgamOBP20 is composed primarily of hydrophobic residues wherein the importance of each residue is herein analysed to further understand the properties of AgamOBP20. This was carried out through computer – aided site – directed mutagenesis coupled with homology modelling and docking simulations wherein each residue in the binding site was changed to alanine and serine. Probable key amino acid residues were identified as LEU106, LEU107, and MET53 which are hypothesized to play a significant role in the protein – ligand interaction. These residues had the greatest impact in the binding free energy when mutated with alanine and serine. The presented results suggest that steric hindrance and hydrophobic interaction are crucial factors to consider on the manner in which the ligand binds with AgamOBP20. The molecular features and parameters obtained may be utilized for the development of new pesticides and repellents that are able to block the function of AgamOBP20 and may result to the disarray of the host – seeking behavior of the Anopheles gambiae.