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 ran ...

s (IUP) containing several repeats of a short

proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the prot ...

-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 most ...

) in their

saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...

. 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 plant ...

mouth feel). Other examples include

Proline-Rich 12 Proline-rich 12 (PRR12) is a protein of unknown function encoded by the gene ''PRR12''. Gene The ''Homo sapiens'' ''PRR12'' gene is 34,785 base pairs long, contains 14 exons, and is located on chromosome 19 at 19q13.33. Known aliases for PRR1 ...

, Proline-Rich Protein 30, and

Proline-Rich Protein 21 Proline-rich protein 21 (PRR21) is a protein of the family of proline-rich proteins. It is encoded by the PRR21 gene, which is found on human chromosome 2, band 2q37.3. The gene exists in several species, both vertebrates and invertebrates, incl ...

References

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