Buffalo nasal odorant-binding protein (bunOBP) and its structural evaluation with putative pheromones

Abstract

Pheromones are odoriferous volatile chemical cues produced by animals for communication among conspecifics so as to regulate their social behaviors. In general, the odor compounds are recognized by receptors in the nasal cavity. Odorant-binding protein (OBP), a lipocalin family protein, mediates the air-borne odor cues to nasal receptors through nasal mucus. The presence of OBP in several mammalian species is well documented but to-date there is no report of a nasal OBP in buffalo. Hence, the present study was undertaken to investigate if OBP is present in buffalo nasal mucus. Uni- and two-dimensional gel electrophoresis of the nasal mucus suggested the presence of OBP, which was confirmed using mass spectrometry. In silico homology model of the OBP was generated and its structural similarity with other mammalian OBPs was assessed. Finally, molecular-docking and -dynamics simulations analysis revealed the efficiency of buffalo nasal OBP (bunOBP) to bind with buffalo pheromones as well as other reported chemical cues. Taken together, the occurrence of nasal OBP in buffalo and its putative role in odor binding are reported for the first time. The potential association of this protein with estrus-specific volatiles could be taken to advantage for non-invasive detection of estrus in buffaloes.

Molecular and functional characterization of buffalo nasal epithelial odorant binding proteins and their structural insights byin-silicoand biochemical approach

“…Among various well-studied pheromones, p-cresol and oleic acid are known to play an important role in the estrus cycle of the female buffalo. These volatiles when perceived by the male buffalo via the nasal lymph help in regulating mating cues [62,28]. In this context, we examined the protein expression, localization, binding characteristics and the site-directed mutagenesis of key residues in typical bnOBPs from the buffalo nasal epithelium, the results of which are consistent with a protein that functions in the recognition of female buffalo sex pheromones.…”

“…In the present study, protein nasal mucus segregated protein from Bos taurus [PDB: 1OBP] shared the maximum sequence identity with bnOBPs and was further chosen as the template for homology modelling. Additionally, it appeared as co-clusters and has maximum evolutionary relationship with buffalo genome [28]. The constructed models were further validated by Pro-CHECK software and visually inspected by PyMOL software tool ( Figure 2).…”

“…Most of the studies suggested that odorant binding proteins are pheromone carriers, either in the certain biological gland or secretary body fluids like urine, saliva, seminal fluid etc. [18,[23][24][25][26][27] as well as also act as a perceiver of olfactory epithelium [17,24,28,21]. Indeed, it has been well established that, these proteins respond to airborne stimuli of pheromones in olfactory systems and trigger adaptive behavioural responses and/or elicit physiological processes [29][30][31] and clearly suggesting a common function to deliver the chemical messengers from the site of production to the external environment.…”

“…Moreover, presence of ligands inside the binding pocket of OBP further increases its thermal stability and seems like a promising attractive feature for designing suitable sensor for biotechnological applications including variety of transducers, gas sensor, quartz crystal microbalance (QCM), surface acoustic wave devices, organic field effect transistors [34][35][36][37][38]. It has also been proposed that, OBPs are expressed in both the nasal mucus and saliva to play important roles in odor perception and sexual communication in buffaloes [26,28]. However, the detailed interaction mechanism between pheromones and OBPs, binding site information as well as structural changes induced by pheromone binding has still remained unclear.…”

“…Based on the reports in buffalo estrus, our long term objective is to construct a biosensor to detect estrus accurately for the effective artificial insemination in buffaloes. The OBP identified and verified in the nasal mucus of buffalo [28] is considered to be the right choice to use this as template to develop biosensor for buffalo estrus detection. Hence, the ultimate aim of this study, to understand of olfaction mechanisms by molecular, biochemical, structural and functional approaches used to determine whether these odorant binding proteins are assisted in perception of sex specific pheromones during the estrus.…”