Factoriin

Factoriin is a fictional protein commonly used in teaching materials to illustrate fundamental concepts in molecular biology and biochemistry. It is not documented as a natural protein in living organisms, and there is no experimental evidence supporting its existence outside pedagogical examples. Because factoriin is illustrative rather than real, descriptions of its properties vary across texts and curricula.

In typical depictions, factoriin is encoded by a hypothetical gene, ftiN, located in a small regulatory operon. The mature polypeptide is shown as a ~60 kilodalton protein that forms a homodimer in its active form. The active site is described as a catalytic region with conserved residues that enable a substrate isomerization reaction, transforming substrate A into product B. There are no entries for factoriin in major protein databases such as UniProt or the Protein Data Bank.

Educational use of factoriin covers topics such as gene expression, protein folding, oligomerization, and enzyme kinetics. Exercises may include constructing synthetic mRNA, predicting folding patterns, and simulating purification and activity assays using fictional data. Because the protein is fictional, reported results are interpretive and intended for instructional purposes rather than real experiments.

Factoriin is often referenced alongside discussions of hypothetical proteins and computational modelling. It provides a neutral example for exploring how scientists infer structure and function from sequence data, and for illustrating the distinction between pedagogical models and empirical biology.