title: Antimicrobial activity against Porphyromonas gingivalis and mechanism of action of the cationic octadecapeptide AmyI-1-18 and its amino acid-substituted analogs.
abstract: The antimicrobial peptide AmyI-1-18 is a cationic α-helical octadecapeptide derived from α-amylase in rice (Oryza sativa L. japonica) that contains four cationic amino acid residues (two arginines and two lysines). To enhance the antibacterial activity of AmyI-1-18 against Porphyromonas gingivalis (a bacterium associated with periodontal disease), we synthesized 12 analogs bearing substitutions with alanine, leucine, and/or arginine that were designed based on helical wheel projections and investigated their antibacterial properties. The antibacterial properties of four analogs bearing substitution of a single arginine or lysine with alanine were almost similar to those of AmyI-1-18, suggesting that the antibacterial properties depend on the presence of three cationic amino acid residues. Of three single arginine-substituted analogs, AmyI-1-18(G12R) exhibited an antibacterial activity 2.8-fold higher [50% growth-inhibitory concentration (IC50): 4.6 μM] than that of AmyI-1-18 (IC50: 13 μM). Likewise, the antibacterial properties of two single leucine-substituted analogs were significantly enhanced; in particular, AmyI-1-18(N3L) exhibited an antibacterial activity (IC50: 2.5 μM) 5.2-fold higher than that of AmyI-1-18. The hemolytic activity of AmyI-1-18(N3L) against mammalian red blood cells was low (2% at 50 μM). A membrane-depolarization assay using a membrane potential-sensitive fluorescent dye revealed that, similar to AmyI-1-18, the antibacterial activity of AmyI-1-18(N3L) was not dependent on its membrane-disrupting activity. Our results demonstrate that the antibacterial properties of AmyI-1-18 against P. gingivalis are significantly improved, without a significant increase in hemolytic activity, by replacing asparagine with leucine at position 3.
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan; Center for Transdisciplinary Research, Niigata University, Niigata 950-2181, Japan. Electronic address: mtanig@eng.niigata-u.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Taniguchi
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Ochiai
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Shun-Ichi
authors.initials: SI
authors.lastname: Nakamichi
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Nomoto
authors.affiliation: Graduate School of Technology, Niigata Institute of Technology, Niigata 945-1195, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Saitoh
authors.affiliation: Department of Chemistry, Tokyo Dental College, Tokyo 101-0062, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D012275:Oryza / Q000737:chemistry / Q000201:enzymology*; D010510:Periodontal Diseases / Q000188:drug therapy / Q000517:prevention & control; D016966:Porphyromonas gingivalis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D012756:Sheep; D000516:alpha-Amylases / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D000516:alpha-Amylases
keywords: Antibacterial peptide; Cationic peptide; Hydrophobicity; Porphyromonas gingivalis; Substitution of amino acid