MUC7 20-Mer: investigation of antimicrobial activity, secondary structure, and possible mechanism of antifungal action.
This study was aimed at examining the spectrum of antimicrobial activity of MUC7 20-mer (N-LAHQKPFIRKSYKCLHKRCR-C; residues 32 to 51 of MUC7, the low-molecular-weight human salivary mucin, comprised of 357 residues) and comparing its antifungal properties to those of salivary histatin 5 (Hsn-5). We also examined the secondary structure of the 20-mer and the possible mechanism of its antifungal action. Our results showed that MUC7 20-mer displays potent killing activity against a variety of fungi and both gram-positive and gram-negative bacteria at micromolar concentrations. Time-dependent killing of Candida albicans and Cryptococcus neoformans by MUC7 20-mer and Hsn-5 indicated differences in killing rates between MUC7 20-mer and Hsn-5. The secondary structure prediction showed that MUC7 20-mer adopts an amphiphilic helix with distinguishable hydrophilic and hydrophobic faces (a characteristic that is associated with antimicrobial activity). In comparison to that of Hsn-5, the fungicidal activity of MUC7 20-mer against C. albicans seems to be independent of fungal cellular metabolic activity, as evidenced by its killing potency at a low temperature (4 degrees C) and in the presence of inhibitors of oxidative phosphorylation in the mitochondrial system. Fluorescence microscopy showed the ability of MUC7 20-mer to cross the fungal cell membrane and to accumulate inside the cells. The internalization of MUC7 20-mer was inhibited by divalent cations. Confocal microscopy of cells doubly labeled with MUC7 20-mer and a mitochondrion-specific dye indicated that mitochondria are not the target of MUC7 20-mer for either C. albicans or C. neoformans.
Bobek
Libuse A
LA
Department of Oral Biology, University at Buffalo, The State University of New York, Buffalo, New York 14214, USA. lbobek@acsu.buffalo.edu
Situ
Hongsa
H
D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003455:Cryptococcus neoformans / Q000187:drug effects*; D016650:Fluorescein-5-isothiocyanate; D054808:Histatins; D006801:Humans; D008826:Microbial Sensitivity Tests; D009077:Mucins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D013329:Structure-Activity Relationship
D000935:Antifungal Agents; C068075:HTN3 protein, human; D054808:Histatins; C083238:MUC7 protein, human; D009077:Mucins; D012471:Salivary Proteins and Peptides; D016650:Fluorescein-5-isothiocyanate