roolein

Roolein is a hypothetical globular protein used in textbooks and computational tutorials to illustrate basic principles of protein structure, folding, and ligand interaction. In standard teaching scenarios, roolein is described as a single-domain protein consisting of roughly 260–290 amino acids, giving a molecular mass around 28–34 kDa. It is assumed to fold into a compact globular structure with a mixed alpha/beta topology, though no experimentally determined structure exists because roolein is not derived from a living organism. Because roolein lacks a natural biological function, researchers use it as a neutral scaffold to study folding pathways, stability, and the effects of mutations without organism-specific context.

In simulations and in silico studies, roolein is often used to test protein design algorithms, to benchmark energy functions, and to explore how sequence variations influence stability and folding landscapes. In some pedagogical variants, roolein is depicted as capable of binding a small aromatic ligand in a hydrophobic pocket, allowing discussion of induced fit and allostery in a simplified setting. Because roolein is a construct rather than a naturally occurring protein, there are no domain organizations or cellular pathways associated with it, and it is not produced by living cells. It serves as a neutral teaching aid to demonstrate core concepts across structural biology, biophysics, and protein engineering.