Major basic protein

A 117-residue protein that predominates in eosinophil granules. It is a potent enzyme against helminths and is toxic towards bacteria and mammalian cells in vitro. The eosinophil major basic protein also causes the release of histamine from mast cells and basophils, activates neutrophils and alveolar macrophages, and is directly implicated in epithelial cell damage, exfoliation and bronchospasm in asthma.

Structurally the major basic protein (MBP) is similar to 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 carbohydrates in the presence of calcium), MBP does not bind either calcium or any of the other carbohydrates that this family recognize.

Instead, MBP recognises heparan sulfate proteoglycans. The structure of MBP is available from the Protein Data Bank, accession number 1h8u and 2brs