Human Neutrophil Granule Cationic Protein CAP37 is a Specific Macrophage Chemotaxin that Shares Homology with Inflammatory Proteinases

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Abstract

Cationic antimicrobial protein CAP37 (Mr = 37 kD) is derived from the azurophilic granules of human PMN. In vitro and in vivo studies demonstrate that CAP37 is a novel monocyte-specific chemoattractant. The N-terminal amino acid sequence of CAP37 shares significant homology with a number of inflammatory molecules with protease activity including elastase and cathepsin G. However, substitutions in the catalytic triad (serine for a histidine at position 41 and glycine for a serine at position 175), may account for its lack of serine protease activity. A full length cDNA for CAP37 was identified in an HL60 cDNA library screened with oligonucleotide probes designed from the N-terminal amino acid sequence. Sequencing of the cDNA reveals a protein of 225 amino acids with significant nucleotide homology to cathepsin G and human neutrophil elastase.