Biochemical interaction of human neutrophil peptide-1 with Mycobacterium tuberculosis H37Ra

The biochemical mechanism of action of human neutrophil peptide-1 (HNP-1) against Mycobacterium tuberculosis H37Ra was studied. Mycobacteria grown in the presence of a subinhibitory concentration (IC50) of HNP-1 showed a significant decrease in the biosynthesis of vital macromolecules, as shown by the incorporation of various radiolabeled precursors. Mycobacterial cells grown in the presence of HNP-1 exhibited surface changes, as was evident from the increased number of binding sites for L-anilinonaphthalene 8-sulfonate. Permeability studies carried out with spheroplasts showed a significantly high permeability to a fluorescent probe, N-phenyl naphthylamine, in the presence of HNP-1. Significant changes in the cell wall and cell membrane were observed when HNP-1-grown cells were analysed by transmission electron microscopy. Our results suggest the mycobacterial cell wall/membrane to be the major target(s) of HNP-1.