Eosinophil granule major basic protein (MBP), a potent toxin for helminths and various cell types, is a 13.8-kD single polypeptide rich in arginine with a calculated isoelectric point (pI) of 10.9. A cDNA for human MBP was isolated from a λ GT10 HL-60 cDNA library. The nucleotide sequence of the MBP cDNA indicates that MBP is translated as a 25.2-kD preproprotein. The 9.9-kD pro-portion of proMBP is rich in glutamic and aspartic acids and has a calculated pI of 3.9, while proMBP itself has a calculated pI of 6.2. We suggest that MBP is translated as a nontoxic precursor that protects the eosinophil from damage while the protein is processed through the endoplasmic reticulum to its sequestered site in the granule core as toxic MBP, and we present results from the literature suggesting that other cationic toxins, which damage cell membranes, may also be processed from nontoxic precursors containing distinct anionic and cationic regions.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Experimental Medicine|
|State||Published - 1988|
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