Zinc-reversible antimicrobial activity of recombinant calprotectin (migration inhibitory factor-related proteins 8 and 14)

Recombinant calprotectin, consisting of 2 individual peptide chains also ca lled migration inhibitory factor-related protein (MRP)-8 and MRP14, was tes ted for antimicrobial activity in a Candida albicans growth inhibition assa y. Both chains contain HEXXH zinc-binding sites and might be expected to ma nifest zinc-reversible, antimicrobial activity similar to that of native ca lprotectin. When tested alone, neither MRP8 nor MRP14 showed activity in th e Candida growth assay. A synthetic 20-amino acid peptide containing the HE XXH sequence of MRP14, along with a nearby HHH sequence, was also inactive in this assay. However, equimolar concentrations of MRP8 and MRP14 demonstr ated a potent growth inhibitory effect that was reversible by 30 mu M zinc. Truncated MRP14 (missing the C-terminal GHH-HKPGLGEGTP tail) used in combi nation with MRP8 demonstrated zinc-reversible activity that was somewhat le ss than that with complete MRP14, These results suggest that intact calprot ectin, consisting of a heterodimer of MRP8 and MRP14, is necessary to form a zinc-binding site capable of inhibiting microbial growth.