Description
Defensins (alpha and beta) are cationic peptides with a broad spectrum of antimicrobial activity that comprise an important arm of the innate immune system. The a-defensins are distinguished from the b-defensins by the pairing of their three disulfide bonds. Four human b-defensins have been identified; BD-1, BD-2, BD-3 and BD-4. B-defensins are expressed on some leukocytes and at epithelial surfaces. In addition to their direct antimicrobial activities, they are chemoattractant towards immature dendritic cells and memory T cells. The B-defensin proteins are expressed as the C-terminal portion of precursors and are released by proteolytic cleavage of a signal sequence and, in the case of BD-1 (36aa), a propeptide region. B-defensins contain a six-cysteine motif that forms three intra-molecular disulfide bonds. B-Defensins are 3-5kD peptides ranging in size from 33-47 amino acid residues. Recombinant Human BD-1 is a 3.9kD protein containing 36 amino acid residues