Mopsin

Mopsin is a fictional protein commonly used in science fiction and educational materials to illustrate principles of membrane biology and signal transduction. It is not a real protein characterized in contemporary biology, nor is it described in peer‑reviewed databases.

In the standard fictional depiction, Mopsin is a membrane-associated receptor with an extracellular ligand-binding domain and a cytoplasmic signaling region. Binding of a hypothetical ligand, referred to as the Mopsin-binding factor (MBF), induces a conformational change that triggers downstream signaling pathways. These pathways are often modeled after well-known signaling cascades, such as G-protein coupled receptor or receptor tyrosine kinase mechanisms, but simplified for instructional purposes. Variants of the concept may portray Mopsin as a single-pass or multi-pass transmembrane protein, and as responsive to different stimuli, including chemical ligands or light.

In educational and speculative contexts, Mopsin serves as a thought experiment to explore structure–function relationships, mutational effects, and the influence of ligand affinity on signaling output. Different narratives may emphasize aspects such as receptor specificity, regulatory feedback, or cross-talk with other cellular pathways, to illustrate common themes in membrane biology.

Because Mopsin is not a real molecule, there are no experimental data, sequences, or three-dimensional structures in public databases. References to Mopsin appear primarily in fictional works, textbooks, and classroom simulations rather than empirical research, and the concept is used to aid understanding of general receptor biology rather than to report real discoveries.