Complementary DNA sequence of human neutrophil azurocidin, an antibiotic with extensive homology to serine proteases.

Human neutrophils contain in their azurophil granules four antibiotic proteins with extensive homology to serine proteases, collectively termed serprocidins. Azurocidin is the only member of the group that lacks proteolytic activity. Using a monospecific antibody, we isolated from human bone marrow a cDNA encoding the complete azurocidin protein in its mature form, along with an N-terminal 24 residue hydrophobic peptide. The N-terminal third of the mature protein sequence contains a cluster of positively charged amino acid residues, many of which are predicted to be surface exposed. The primary sequence is highly homologous to elastase, proteinase 3, cathepsin G, T-cell granzymes and other serine proteases. However, azurocidin has Gly for Ser and Ser for His substitutions in the catalytic triad. Southern blot analysis of human genomic DNA suggests the existence of a single azurocidin coding sequence.