Moricin, a Novel Type of Antibacterial Peptide Isolated from the Silkworm, Bombyx mori

Abstract

A novel antibacterial peptide that shows antibacterial activity against Staphylococcus aureus was isolated from the hemolymph of the silkworm, Bombyx mori. The novel peptide consisted of 42 amino acids and was highly basic. This peptide indicated no significant similarity with other antibacterial peptides. The peptide showed antibacterial activity against several Gram-negative and -positive bacteria and had a higher activity against Gram-positive bacteria than cecropin B 1 , a major antibacterial peptide of B. mori. The novel peptide was inducible by bacterial injection. These results suggest that the peptide is responsible for the antibacterial activity in B. mori against Gram-positive bacteria. The effects of the peptide on bacterial and liposomal membranes showed that a target of the peptide is the bacterial cytoplasmic membrane. The results also suggest that the N-terminal portion of the peptide, containing a predicted ␣-helix, is responsible for an increase in the membrane permeability. We propose the name "moricin" for this novel antibacterial peptide isolated from B. mori.

A genome-wide analysis of antimicrobial effector genes and their transcription patterns in Manduca sexta

“…Moricins are cationic AMPs, which kill Gram-positive and -negative bacteria at low concentrations and have been found only in lepidopteran insects (Hara and Yamakawa, 1995a; Yi et al, 2014). Similar to cecropins, moricin maturation may involve signal peptide removal, amino dipeptidase processing, and C-terminal amidation by processing of a Gly residue (Fig.…”

Solution structure, antibacterial activity, and expression profile of Manduca sexta moricin

“…While defensins are found in several orders of insects (Diptera, Hymenoptera, Coleoptera, Trichoptera, Hemiptera, and Odonata) and are highly effective against Grampositive bacteria, they have not been found in any lepidopteran species. Instead, a unique group of AMPs named moricins are identified in moths, which kill Gram-positive and Gram-negative bacteria at a low micromolar range [7,9,12]. Moricins drastically differ in tertiary structure from defensins that are stabilized by three disulfide bonds [30].…”

“…Exclusively found in lepidopteran insects so far, moricin-like AMPs are active against both Gram-positive and Gram-negative bacteria [9]. They affect structural integrity of bacterial plasma membrane.…”

Insect antimicrobial peptides and their applications

“…Moricin was first isolated from the hemolymph of E. coli -immunized B. mori larvae as a highly basic 42-residue peptide (Hara and Yamakawa, 1995a). Moricin has been found only in Lepidopteran insects so far, and cDNAs encoding moricins have been identified in M. sexta (Zhu et al, 2003), Spodoptera litura (Oizumi et al, 2005), G. mellonella (Brown et al, 2008), H. armigera (Wang et al, 2010b), S. exigua, H. virescens , and Hyblaea puera (cDNA sequences are available in the NCBI database).…”

“…Moricins have activity against Gram-negative and Gram-positive bacteria, and G. mellonella moricins also show high activity against filamentous fungi and yeast (Brown et al, 2008; Dai et al, 2008; Hara and Yamakawa, 1995a). The tertiary solution structures of moricins show a long α-helix with 8 turns along nearly the full length peptide, except for a few residues at the N- and C-terminal regions (Dai et al, 2008; Hemmi et al, 2002; Oizumi et al, 2005) (Fig.…”