Major basic protein

Proteoglycan 2, bone marrow (natural killer cell activator, eosinophil granule major basic protein), also known as PRG2, is a is_associated_with::protein which in humans is encoded by the PRG2 is_associated_with::gene.

Function
The protein encoded by this gene is the predominant constituent of the crystalline core of the is_associated_with::eosinophil granule. High levels of the proform of this protein are also present in placenta and pregnancy serum, where it exists as a complex with several other proteins including pregnancy-associated plasma protein A (PAPPA), angiotensinogen (AGT), and C3dg. This protein may be involved in antiparasitic defense mechanisms as a is_associated_with::cytotoxin and is_associated_with::helminthotoxin, and in immune hypersensitivity reactions. It is directly implicated in epithelial cell damage, exfoliation, and is_associated_with::bronchospasm in allergic diseases.

PRG2 is a 117-residue protein that predominates in is_associated_with::eosinophil granules. It is a potent enzyme against is_associated_with::helminths and is toxic towards bacteria and mammalian cells in vitro. The is_associated_with::eosinophil major basic protein also causes the release of is_associated_with::histamine from is_associated_with::mast cells and is_associated_with::basophils, and activates is_associated_with::neutrophils and alveolar is_associated_with::macrophages.

Structure
Structurally the major basic protein (MBP) is similar to is_associated_with::lectins (sugar-binding proteins), and has a fold similar to that seen in C-type lectins. However, unlike other C-type lectins (those that bind various is_associated_with::carbohydrates in the presence of is_associated_with::calcium), MBP does not bind either calcium or any of the other carbohydrates that this family recognize.

Instead, MBP recognises is_associated_with::heparan sulfate is_associated_with::proteoglycans. Two crystallographic structures of MBP have been determined.

Interactions
Major basic protein has been shown to interact with is_associated_with::Pregnancy-associated plasma protein A.