DOI: https://doi.org/10.36347/sajb.2025.v13i12.004

Pages: 1589-1603

Melatonin is an indoleamine hormone primarily produced by the pineal gland. It plays a vital role in regulating circadian rhythms, sleep–wake cycles, and several physiological functions, including antioxidant defense and immune response. Its effects are mediated through G protein–coupled receptors, mainly MT1 and MT2, which show structural and functional differences across species. To conduct this analysis, several bioinformatics tools were used: receptor sequences were retrieved from NCBI in FASTA format; interaction profiles and binding affinities were assessed using the STRING database; 3D structural models were predicted with Phyre2; and molecular visualizations were evaluated using Biovia Discovery Studio (BDS). This study presents a comparative bioinformatics analysis of melatonin–receptor interactions in humans, rats, and fish. The aim is to investigate evolutionary conservation and species-specific variations in receptor structure and ligand binding, which may affect receptor sensitivity and downstream signaling pathways. The results revealed distinct differences in binding site residues and interaction energies among the species, indicating evolutionary adaptations in receptor function. These findings offer valuable insights into the molecular diversity of melatonin signaling and may support the development of species-specific receptor-targeted therapeutics.