An Evolutionary Conserved Ethephon Binding Site Bridges the Gap Between Human and Rat Acetylcholinesterase Article Swipe
Wistar rats are used to study organophosphate toxicity on Acetylcholinesterase (AChE) and predict their effects on humans. The present study attempts to validate the use of Wistar rats at a molecular level. A comparative study of the two organisms’ AChE coding polypeptide sequences was performed using phylogenetics and multiple sequence alignment. Subsequently on establishing an evolutionary relatedness between the AChE macro-molecules a comparative analysis using homology modelling and virtual screening techniques was performed. Upon confirmation of the mechanism of organophosphate toxicity, the tests were confirmed with in-vivo testing using ethephon, a commonly used organophosphate fruit ripener). Wistar rats (n=6) were gavaged either with 3 doses (100, 250, 500 mg/kg) of ethephon or distilled water for 90 days (ethical no: 24/14). On day 91, AChE activity was determined. Analysis revealed the polypeptide sequence coding for AChE is evolutionarily conserved to a degree in the mammalian clade. The tertiary structures of Rattus norvegicus and Homo sapiens shared a low RMSD value of 0.359. Virtual screening revealed that the binding mechanism of the organophosphate dubbed ethephon was evolutionary conserved with the ligand having the same orientation in both accounts. The binding site consisted of five evolutionary conserved sequence motifs namely GG, Y, F, YF, and H. The AChE activity in 100, 250 and 500 mg/kg of ethephone treated animals were significantly (p<0.05) lowered by 5.8%, 9.9% and15.8% respectively when compared to control group. The study was able to conclusively validate the use of Wistar rats as a model organism representing humans in the inhibition of AChE by the organophosphate ethephon.
