Tubby protein

The tubby protein is an upstream cell signaling protein common to multicellular eukaryotes. The original tubby gene was identified in mice, but proteins that are homologous to tubby are known as "tubby-like proteins" (TULPs) and share a common and characteristic tertiary structure that consists of a beta barrel packed around an alpha helix in the central pore. The protein derives its name from its role in metabolism; mice with mutated tubby genes suffer from obesity.

Structure
Tubby proteins are classified as α+β proteins and have a 12-beta stranded barrel surrounding a central alpha helix. Tubby proteins can bind the small cell signaling molecule phosphatidylinositol, which is typically localized to the cell membrane.

Function
Tubby proteins have been implicated as transcription factors and as potential signaling factors coupled to G-protein activity. They are associated with neuronal differentiation and development, and in mammals are implicated in three disease processes when mutated: obesity, retinal degeneration, and hearing loss. In mice, mutations in tubby proteins are known to affect lifespan and fat storage as well as carbohydrate metabolism. Tubby domains associate with cytoplasmic side of cell membranes through binding of different phosphoinositides