Proline-rich proteins (PRPs) is a class of

intrinsically unstructured protein In molecular biology, an intrinsically disordered protein (IDP) is a protein that lacks a fixed or ordered three-dimensional structure, typically in the absence of its macromolecular interaction partners, such as other proteins or RNA. IDPs r ...

s (IUP) containing several repeats of a short proline-rich sequence. Many

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner ...

-consuming animals secrete a tannin-binding protein (

mucin Mucins () are a family of high molecular weight, heavily glycosylated proteins ( glycoconjugates) produced by epithelial tissues in most animals. Mucins' key characteristic is their ability to form gels; therefore they are a key component in m ...

) in their saliva. Tannin-binding capacity of salivary mucin is directly related to its proline content. Advantages in using salivary proline-rich proteins (PRPs) to inactivate tannins are : * PRPs inactivate tannins to a greater extent than do dietary proteins; this results in reduced fecal nitrogen losses, * PRPs contain non specific nitrogen and nonessential amino acids; this makes them more convenient for an animal to exploit rather than using up valuable dietary protein. Example of this class of protein is IB5, a human parotid salivary protein known to bind with polyphenols (binding responsible for the

astringency An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissues. The word derives from the Latin ''adstringere'', which means "to bind fast". Calamine lotion, witch hazel, and yerba mansa, a Californian pl ...

mouth feel). Other examples include Proline-Rich 12, Proline-Rich Protein 30, and Proline-Rich Protein 21.

References

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