Antimicrobial Peptides (AMPs) with Dual Mechanisms: Membrane Disruption and Apoptosis
Antimicrobial Peptides (AMPs) with Dual Mechanisms: Membrane Disruption and Apoptosis
Journal of Microbiology and Biotechnology. 2015. Jun, 25(6): 759-764
Copyright © 2015, The Korean Society For Microbiology And Biotechnology
  • Received : November 21, 2014
  • Accepted : December 19, 2014
  • Published : June 28, 2015
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Juneyoung Lee
Dong Gun Lee

Antimicrobial peptides (AMPs) are one of the critical components in host innate immune responses to imbalanced and invading microbial pathogens. Although the antimicrobial activity and mechanism of action have been thoroughly investigated for decades, the exact biological properties of AMPs are still elusive. Most AMPs generally exert the antimicrobial effect by targeting the microbial membrane, such as barrel stave, toroidal, and carpet mechanisms. Thus, the mode of action in model membranes and the discrimination of AMPs to discrepant lipid compositions between mammalian cells and microbial pathogens (cell selectivity) have been studied intensively. However, the latest reports suggest that not only AMPs recently isolated but also well-known membrane-disruptive AMPs play a role in intracellular killing, such as apoptosis induction. In this mini-review, we will review some representative AMPs and their antimicrobial mechanisms and provide new insights into the dual mechanism of AMPs.
Antimicrobial peptides (AMPs) are multifunctional molecules produced by not only specific cells but also many tissues of animals, plants, and invertebrates. They consist of diverse amino acids and are generally characterized by their size, sequence, net charge, structure, hydrophobicity, and amphipathicity [4] . Briefly, AMPs have approximately 12 to 50 amino acids and secondary structures like α-helix, β-sheet, or relaxed coils. Cationic antimicrobial peptides (CAPs) possess abundant positively charged amino acids, such as arginine (R) and lysine (K). The cationicity is specifically involved in the antibacterial activity, because the attraction between CAPs and the negatively charged head group of some phospholipids in the bacterial outer membrane, such as phosphatidylglycerol (PG) and cardiolipin, or lipopolysaccharide (LPS), and teichoic acid, is the first step for exerting antibacterial activity, followed by the interaction, insertion, and the membrane perturbation [46] . The hydrophobicity, relating to specific hydrophobic amino acids like tryptophan (W) or phenylalanine (F), is another significant factor, in terms of the affinity of water-soluble AMPs with target membrane lipid bilayer [4] , which results in the antimicrobial effect. The hydrophobic region, such as hydrophobic terminus or hydrophobic amino acids, is also related to the self-association, forming α-helical bundles of AMPs [47] . It can additionally contribute to the toxicity of AMPs towards host cells. Therefore, designing cell-selective potent analogue peptides with reduced toxicity is a significant issue in peptide engineering study [23] . Owing to their unique properties, AMPs can be regarded as a novel pharmaceutical candidate for treating the diseases caused by pathogenic bacterial and fungal species, antibiotic-resistant microbial species, and even cancers.
AMPs Possessing Membrane-Active Mechanism
As is well known, AMPs exert their activity on microbial membrane or intracellular compartments. Specifically, membrane-disruptive peptides have been focused on thoroughly because of their direct potent activity against microbial plasma membranes. In the following subsections, we briefly review some key membrane-active AMPs ( Table 1 ).
AMPs and their antimicrobial mechanisms.
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AMPs and their antimicrobial mechanisms.
- Defensins and Cathelicidins
In mammals, the epithelium of the intestine, respiratory tract, or skin is the first line of defense regarding barrier function and homeostasis because it directly adjoins an external environment [11] . Therefore, antimicrobial proteins derived from epithelial cells (ECs) are thoroughly investigated in the epithelial cell defense system. Defensins are the most well-established AMPs, consisting of 30-40 amino acids containing six cysteine residues [12 , 31] . They consist of two major groups, α-defensins and β-defensins.
α-Defensins are highly expressed in the small intestine. HD5 (DEFA5) and HD6 (DEFA6) peptides in humans are representative α-defensins [39] . Cryptdins are murine α-defensins [39] . α-Defensins are small peptides containing conserved amphipathic structures with positively charged/ hydrophobic residues [52] . This structural feature allows these peptides to bind with negatively charged cell surfaces of invading pathogens and to be inserted into the membrane [52] .
β-Defensins are secreted from the epithelium of the skin (keratinocytes), respiratory tract (respiratory ECs), and large intestine (mainly enterocytes) [11] . This group of AMPs also exerts antimicrobial activity through selective microbial membrane permeabilization [45] . Cathelicidins ( e.g. , LL37 in humans and CRAMP in mice) are abundant in resident mast cells of the skin and also exist in ECs of the lung, urinary tract, and large intestine [2] . They are generally cationic α-helical peptides and these properties contribute to the binding affinity between cathelicidins and negatively charged phospholipids of bacteria [2] .
Paneth cells are specialized secretory cells residing at the base of small intestinal crypts [41] . For intestinal homeostasis, they produce the antimicrobial proteins against enteric pathogens, such as α-defensins (cryptdins in mice), cryptdinrelated sequence (CRS) peptide, regenerating islet-derived protein (Reg) family of C-type lectins, and lysozymes [5 , 7 , 38] . HIP/PAP, hepatointestinal pancreatic/pancreatitis-associated protein (Reg3α) in humans and Reg 3β and Reg3 γ in mice are representatives of the Reg family [38] . They have carbohydrate recognition domains selectively recognizing peptidoglycan of the gram-positive bacterial cell wall [30] . They are not membrane-disruptive AMPs. However, they play critical roles by interacting with the cell surface of bacteria.
- Melittin
Melittin is the most distinguished lytic peptide, which is the main component of bee venom (40-50%) isolated from honey bee Apis mellifera [13] . This α-helical peptide is hydrophobic and possesses a high positive net charge of +6 [9] . It is generally used for membrane studies as a control peptide, as it exhibits definite disruption of the lipid membrane. Briefly, melittin binds to lipid membranes and forms a α-helical structure with both parallel and perpendicular positions. The perpendicular position is thought to be involved in pore formation [14 , 16 , 28 , 33 , 49 , 50] . Characteristically, melittin as a monomer, over 1 μg/ml, can bind to membrane lipids of erythrocytes, resulting in hemoglobin release within a few seconds [15] . Therefore, the design of analogs with lower cytotoxicity is important in melittin studies. Many studies focused on the leucine zipper motif contributing to the toxicity towards mammalian cells and simultaneous nonselective activity [40 , 53] .
- Cecropin
Cecropins were the first insect AMPs isolated from a giant silk moth, Hyalophora cecropia [17] . This peptide is cationic and adopts α-helical structures in the hydrophobic condition. Cecropins display a broad spectrum of antibacterial activity against gram-negative and gram-positive bacterial strains, and originate from the amidated C-terminus conferring to the interaction between membranes and these peptides [32 , 37] . Christensen et al . [8] demonstrated in detail that cecropins interacted with the lipid bilayer with electrostatic adsorption, followed by the insertion of the hydrophobic C-terminus in contrast with residual amphipathic helix in the interface. Moreover, cecropin showed channel formation in membranes in a voltage-dependent manner [8] . In mammals, cecropin P1 derived from the porcine small intestine has similarity in amino acids with insect cecropins [27] . Cecropins are also used as a reference peptide, like melittin, in membrane studies and antimicrobial mechanism studies of peptides and proteins. As is well-documented, cecropin A/melittin (CAME) hybrid peptides are established analog AMPs showing advanced antimicrobial effects [3 , 36] .
- Magainin
In 1987, Zasloff [51] designated the magainin peptides (magainin 1 and magainin 2), which originated from the skin of Xenopus laevis , an African clawed frog [51] . Interestingly, he suggested these AMPs could be expressed in not only eosinophilic and granule-laden intestinal cells, like mammalian Paneth cells, of Xenopus small intestine, but also the skin [43] . This site specificity suggested that magainins play a conserved role in the host defense system in both mammalians and non-mammalian vertebrates [43 , 51] . These two 23 mer peptides have an α-helical structure and a net positive charge of +4 [51] . They also showed remarkable antibiotic activity against a broad spectrum of bacteria, fungi, and protozoa [51] . Magainins have been thoroughly investigated regarding their biological properties and their notable features. They show high cell selectivity between pathogens and mammalian cells at the concentrations exhibiting antimicrobial activities, which allowed them to be employed as a template for the design of novel analog peptides [6 , 35 , 51] . In terms of the mechanism of action, magainins bind to acidic lipid compositions through electrostatic interactions and permeabilize the cell plasma membrane by forming pores [34 , 35] . The analog of cecropin A/magainin 2 (CAMA) hybrid peptide, an antibacterial peptide [48] , is still being investigated for its clinical potential in microbial diseases in humans [44] .
AMPs Possessing Apoptosis-Inducing Mechanism
In this part, we introduce some AMPs containing the apoptosis-inducing mechanism. Additionally, the established membrane-active AMPs showing a dual mechanism are reviewed ( Table 1 ).
- Coprisin
Coprisin (VTCDVLSFEAKGIAVNHSACALHCIALRKK GGSCQNGVCVCRN-NH 2 ) is a defensin-like 43 mer peptide containing three disulfide bonds (positions: 3-34, 20-39, and 24-41), which was isolated from the dung beetle, Copris tripartitus , in 2009 [19] . Coprisin exhibited broad-spectrum antifungal activities against various fungal pathogens, such as Aspergillus and Candida species, without any cytotoxicity towards human erythrocytes [26] . Interestingly, several membrane studies, such as 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence analysis, calcein leakage measurement from large unilamellar vesicles (LUVs), and rhodamine-conjugated single giant unilamellar vesicle (GUV) analysis, suggested that coprisin did not disrupt both the cell plasma membrane of Candida albicans and fungal model membranes [26] . Notably, in a rhodamine-conjugated single GUV, which is consisted of phosphatidylchoine (PC)/phosphatidylethanolamine (PE)/phosphatidylinositol (PI)/ergosterol (5:4:1:2 (w/w/w/w)), the absence of membrane-active action was well visualized [26] . Therefore, it was hypothesized that coprisin exerted its activity after the cell penetration. Based on the hypothesis, some apoptosis markers, such as phosphatidylserine (PS) exposure for early apoptosis, and DNA fragmentation for late apoptosis, were examined. The results showed that corpisin significantly induced apoptosis in C. albicans [26] . Furthermore, reactive oxygen species (ROS), specifically hydroxyl radicals (• OH), are suggested as key players in coprisin-induced apoptosis [26] . Coprisin additionally caused mitochondrial dysfunction and cytochrome c release/caspase activation as downstream events [26] . In addition, in terms of antibacterial activity, coprisin, which possesses an amphipathic α-helix (A 19 to R 28 ) and a electropositive surface formed by R 28 , K 29 , K 30 , and R 42 , showed potent activity by targeting bacterial LPS [22] . However, the antifungal study of coprisin provided new insight regarding the mechanism of AMPs.
- Papiliocin
In 2010, a novel cecropin-like AMP was isolated by Kim et al . [21] and named papiliocin. Papiliocin (RWKIFKKIE KVGRNVRDGIIKAGPAVAVVGQAATVVK-NH 2 ) is a 37 mer peptide isolated from the swallowtail butterfly, Papilio xuthus [21] . It exhibited potent antimicrobial activities against both gram-positive and negative bacteria, and fungi, without cytotoxicity against human erythrocytesv [21] . The first mechanism study of paliliocin showed that papiliocin effectively disrupted the fungal plasma membrane of C. albicans [25] . In model membranes mimicking the outer leaflets of the C. albicans plasma membrane, papiliocin formed pores on the membrane within minutes [25] . The secondary structure, and antibacterial and anti-inflammatory properties of papiliocin were further investigated [20] . Kim et al . [20] suggested that papiliocin contained two α-helices (K 3 to K 21 and A 25 to V 36 ) with the hinge region [20] .
The novel antimicrobial mechanism of papiliocin was proposed in succession [18] . The results showed that papiliocin caused apoptotic events, such as PS flip-flop, chromatin condensation, and DNA fragmentation in C. albicans [18] . It was also suggested that ROS accumulation and mitochondrial membrane damage could be the key in papiliocin-induced fungal apoptosis [18] . Unlike coprisin, papiliocin peptide showed a dual mechanism, membrane-active action, and apoptosis induction, specifically in fungal pathogens [18 , 25] . The exact demonstration of the coexistence between two discrepant mechanisms is still largely unknown. However, it will enable more effective clinical approaches in treating human fungal disease.
- Melittin
As noted previously, melittin is widely known as a membrane-active AMP. However, a novel antimicrobial mechanism of melittin has been suggested [24] . In 2010, the potential of melittin in C. albicans was suggested for the first time by using some hallmarks of apoptosis, such as Annexin V, DAPI, and TUNEL staining [42] . However, the in-depth mechanism was still elusive. In 2014, the intracellular mechanism of melittin-induced apoptosis in C. albicans was further characterized [24] . Melittin caused ROS generation to play a pivotal role in the apoptosis induction, and specifically OH is significantly involved [24] . The results also suggested the mitochondrial dysfunction and the caspase activation induced by melittin and further indicated the role of mitochondria by investigating Ca 2+ homeostasis between the ER and mitochondria [24] . In the study, mitochondrial Ca 2+ levels were highly increased, suggesting the mitochondrial perturbation or rupture by the decreased mitochondrial membrane potential (∆Ψ m ) [24] . In summary, it was suggested that melittin also possessed a dual antifungal mechanism.
- Magainin 2
As discussed previously, magainin 2 is a pore-forming AMP [34 , 35] . It was recently proposed that magainin 2 caused bacterial cell death in Escherichia coli , like eukaryotic apoptosis [29] . Magainin 2 showed the apoptotic phenotype in a caspase-dependent manner, after membrane disruption [29] . Furthermore, RecA protein, which is essential for DNA repair in bacterial SOS responses [10] , was suggested as a key player in magainin 2-induced bacterial cell death [29] . The result suggested that RecA was involved in the cleavage of LexA protein, which regulates SOS response in the damaged bacteria [1 , 29] , and that RecA also acted as a caspase substrate in this apoptosis-like death [29] . It suggests that membrane-active peptides can successively exert the antimicrobial activity.
In conclusion, we have reviewed several membrane-active AMPs and comparatively novel AMPs showing apoptosis-inducing ability ( Fig. 1 ). As noted, AMPs are still the most potent candidates as alternatives of conventional antibiotics. Ongoing studies, in terms of understanding the diverse mechanism of AMP, will contribute to the development of more potent AMPs without unexpected side effects.
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Dual mechanisms of AMPs.
This work was supported by a grant from the Next-Generation BioGreen 21 Program (No. PJ01104303), Rural Development Administration, Republic of Korea.
Adikesavan AK , Katsonis P , Marciano DC , Lua R , Herman C , Lichtarge O. 2011 Separation of recombination and SOS response inEscherichia coliRecA suggests LexA interaction sites. PLoS Genet 7 e1002244 -    DOI : 10.1371/journal.pgen.1002244
Bals R , Wilson JM. 2003 Cathelicidins – a family of multifunctional antimicrobial peptides. Cell. Mol. Life Sci. 60 711 - 720    DOI : 10.1007/s00018-003-2186-9
Boman HG , Wade D , Boman IA , Wåhlin B , Merrifield RB 1989 Antibacterial and antimalarial properties of peptides that are cecropin-melittin hybrids. FEBS Lett. 259 103 - 106    DOI : 10.1016/0014-5793(89)81505-4
Brogden KA 2005 Antimicrobial peptides: pore formers or metabolic inhibitors in bacteria? Nat. Rev. Microbiol. 3 238 - 250    DOI : 10.1038/nrmicro1098
Cash HL , Whitham CV , Behrendt CL , Hooper LV 2006 Symbiotic bacteria direct expression of an intestinal bactericidal lectin. Science 313 1126 - 1130    DOI : 10.1126/science.1127119
Chen HC , Brown JH , Morell JL , Huang CM 1988 Synthetic magainin analogues with improved antimicrobial activity. FEBS Lett. 236 462 - 466    DOI : 10.1016/0014-5793(88)80077-2
Christa L , Carnot F , Simon MT , Levavasseur F , Stinnakre MG , Lasserre C 1996 HIP/PAP is an adhesive protein expressed in hepatocarcinoma, normal Paneth, and pancreatic cells. Am. J. Physiol. 271 G993 - G1002
Christensen B , Fink J , Merrifield RB , Mauzerall D 1988 Channel-forming properties of cecropins and related model compounds incorporated into planar lipid membranes. Proc. Natl. Acad. Sci. USA 85 5072 - 5076    DOI : 10.1073/pnas.85.14.5072
Dempsey CE 1990 The actions of melittin on membranes. Biochim. Biophys. Acta 1031 143 - 161    DOI : 10.1016/0304-4157(90)90006-X
Dwyer DJ , Camacho DM , Kohanski MA , Callura JM , Collins JJ 2012 Antibiotic-induced bacterial cell death exhibits physiological and biochemical hallmarks of apoptosis. Mol. Cell 46 561 - 572    DOI : 10.1016/j.molcel.2012.04.027
Gallo RL , Hooper LV 2012 Epithelial antimicrobial defence of the skin and intestine. Nat. Rev. Immunol. 12 503 - 516    DOI : 10.1038/nri3228
Ganz T 2003 Defensins: antimicrobial peptides of innate immunity. Nat. Rev. Immunol. 3 710 - 720    DOI : 10.1038/nri1180
Habermann E 1972 Bee and wasp venoms. Science 177 314 - 322    DOI : 10.1126/science.177.4046.314
He K , Ludtke SJ , Heller WT , Huang HW 1996 Mechanism of alamethicin insertion into lipid bilayers. Biophys. J. 71 2669 - 2679    DOI : 10.1016/S0006-3495(96)79458-4
Hider RC , Khader F , Tatham AS 1983 Lytic activity of monomeric and oligomeric melittin. Biochim. Biophys. Acta 728 206 - 214    DOI : 10.1016/0005-2736(83)90473-X
Hristova K , Dempsey CE , White SH 2001 Structure, location, and lipid perturbations of melittin at the membrane interface. Biophys. J. 80 801 - 811    DOI : 10.1016/S0006-3495(01)76059-6
Hultmark D , Steiner H , Rasmuson T , Boman HG 1980 Insect immunity. Purification and properties of three inducible bactericidal proteins from hemolymph of immunized pupae ofHyalophora cecropia. Eur. J. Biochem. 106 7 - 16    DOI : 10.1111/j.1432-1033.1980.tb05991.x
Hwang B , Hwang JS , Lee J , Kim JK , Kim SR , Kim Y 2011 Induction of yeast apoptosis by an antimicrobial peptide, papiliocin. Biochem. Biophys. Res. Commun. 408 89 - 93
Hwang JS , Lee J , Kim YJ , Bang HS , Yun EY , Kim SR 2009 Isolation and characterization of a defensin-like peptide (coprisin) from the dung beetle,Copris tripartitus. Int. J. Pept.    DOI : 10.1155/2009/136284.
Kim JK , Lee E , Shin S , Jeong KW , Lee JY , Bae SY 2011 Structure and function of papiliocin with antimicrobial and anti-inflammatory activities isolated from the swallowtail butterfly,Papilio xuthus. J. Biol. Chem. 286 41296 - 41311    DOI : 10.1074/jbc.M111.269225
Kim SR , Hong MY , Park SW , Choi KH , Yun EY , Goo TW 2010 Characterization and cDNA cloning of a cecropin-like antimicrobial peptide, papiliocin, from the swallowtail butterfly,Papilio xuthus. Mol. Cells 29 419 - 423    DOI : 10.1007/s10059-010-0050-y
Lee E , Kim JK , Shin S , Jeong KW , Shin A , Lee J 2013 Insight into the antimicrobial activities of coprisin isolated from the dung beetle,Copris tripartitus, revealed by structure-activity relationships. Biochim. Biophys. Acta Biomembr. 1828 271 - 283    DOI : 10.1016/j.bbamem.2012.10.028
Lee J , Choi H , Cho J , Lee DG 2011 Effects of positively charged arginine residues on membrane pore forming activity of Rev-NIS peptide in bacterial cells. Biochim. Biophys. Acta Biomembr. 1808 2421 - 2427    DOI : 10.1016/j.bbamem.2011.06.024
Lee J , Lee DG 2014 Melittin triggers inCandida albicansthrough the reactive oxygen species-mediated mitochondria/caspase-dependent pathway. FEMS Microbiol. Lett. 355 36 - 42    DOI : 10.1111/1574-6968.12450
Lee J , Hwang JS , Hwang B , Kim JK , Kim SR , Kim Y 2010 Influence of the papiliocin peptide derived fromPapilio xuthuson the perturbation of fungal cell membranes. FEMS Microbiol. Lett. 311 70 - 75    DOI : 10.1111/j.1574-6968.2010.02073.x
Lee J , Hwang JS , Hwang IS , Cho J , Lee E , Kim Y 2012 Coprisin-induced antifungal effects inCandida albicanscorrelate with apoptotic mechanisms. Free Radic. Biol. Med. 52 2302 - 2311    DOI : 10.1016/j.freeradbiomed.2012.03.012
Lee JY , Boman A , Sun CX , Andersson M , Jörnvall H , Mutt V 1989 Antibacterial peptides from pig intestine: isolation of a mammalian cecropin. Proc. Natl. Acad. Sci. USA 86 9159 - 9162    DOI : 10.1073/pnas.86.23.9159
Lee MT , Hung WC , Chen FY , Huang HW 2008 Mechanism and kinetics of pore formation in membranes by water-soluble amphipathic peptides. Proc. Natl. Acad. Sci. USA 105 5087 - 5092    DOI : 10.1073/pnas.0710625105
Lee W , Lee DG 2014 Magainin 2 induces bacterial cell death showing apoptotic properties. Curr. Microbiol. 69 794 - 801    DOI : 10.1007/s00284-014-0657-x
Lehotzky RE , Partch CL , Mukherjee S , Cash HL , Goldman WE , Gardner KH 2010 Molecular basis for peptidoglycan recognition by a bactericidal lectin. Proc. Natl. Acad. Sci. USA 107 7722 - 7727    DOI : 10.1073/pnas.0909449107
Lehrer RI 2004 Primate defensins. Nat. Rev. Microbiol. 2 727 - 738    DOI : 10.1038/nrmicro976
Li ZQ , Merrifield RB , Boman IA , Boman HG 1988 Effects on electrophoretic mobility and antibacterial spectrum of removal of two residues from synthetic sarcotoxin IA and addition of the same residue to cecropin B. FEBS Lett. 231 299 - 302    DOI : 10.1016/0014-5793(88)80837-8
Ludtke SJ , He K , Heller WT , Harroun TA , Yang L , Huang HW 1996 Membrane pores induced by magainin. Biochemistry 35 13723 - 13728    DOI : 10.1021/bi9620621
Matsuzaki K , Harada M , Funakoshi S , Fujii N , Miyajima K 1991 Physicochemical determinants for the interactions of magainins 1 and 2 with acidic lipid bilayers. Biochim. Biophy. Acta 1063 162 - 170    DOI : 10.1016/0005-2736(91)90366-G
Matsuzaki K , Sugishita K , Harada M , Fujii N , Miyajima K 1997 Interactions of an antimicrobial peptide, magainin 2, with outer and inner membranes of gram-negative bacteria. Biochim. Biophy. Acta 1327 119 - 130    DOI : 10.1016/S0005-2736(97)00051-5
Merrifield RB , Juvvadi P , Andreu D , Ubach J , Boman A , Boman HG 1995 Retro and retroenantio analogs of cecropin-melittin hybrids. Proc. Natl. Acad. Sci. USA 92 3449 - 3453    DOI : 10.1073/pnas.92.8.3449
Nakajima Y , Qu XM , Natori S 1987 Interaction between liposomes and sarcotoxin IA, a potent antibacterial protein ofSarcophaga peregrina(flesh fly). J. Biol. Chem. 262 1665 - 1669
Ogawa H , Fukushima K , Naito H , Funayama Y , Unno M , Takahashi K 2003 Increased expression of HIP/PAP and regenerating gene III in human inflammatory bowel disease and a murine bacterial reconstitution model. Inflamm. Bowel Dis. 9 162 - 170    DOI : 10.1097/00054725-200305000-00003
Ouellette AJ 2011 Paneth cell α-defensins in enteric innate immunity. Cell. Mol. Life Sci. 68 2215 - 2219    DOI : 10.1007/s00018-011-0714-6
Pandey BK , Ahmad A , Asthana N , Azmi S , Srivastava RM , Srivastava S 2010 Cell-selective lysis by novel analogues of melittin against human red blood cells andEscherichia coli. Biochemistry 49 7920 - 7929    DOI : 10.1021/bi100729m
Paneth J 1887 Ueber die secernirenden Zellen des Dünndarm-Epithels. Arch. Mikrosk. Anat. 31 113 - 191    DOI : 10.1007/BF02955706
Park C , Lee DG 2010 Melittin induces apoptotic features inCandida albicans. Biochem. Biophys. Res. Commun. 394 170 - 172    DOI : 10.1016/j.bbrc.2010.02.138
Reilly DS , Tomassini N , Bevins CL , Zasloff M 1994 A Paneth cell analogue inXenopussmall intestine expresses antimicrobial peptide genes: conservation of an intestinal host-defense system. J. Histochem. Cytochem. 42 697 - 704    DOI : 10.1177/42.6.8189032
Ryu S , Choi SY , Acharya S , Chun YJ , Gurley C , Park Y 2011 Antimicrobial and anti-inflammatory effects of cecropin A(1-8)-magainin2(1-12) hybrid peptide analog p5 againstMalassezia furfurinfection in human keratinocytes. J. Invest. Dermatol. 131 1677 - 1683    DOI : 10.1038/jid.2011.112
Schmidt NW , Mishra A , Lai GH , Davis M , Sanders LK , Tran D 2011 Criterion for amino acid composition of defensins and antimicrobial peptides based on geometry of membrane destabilization. J. Am. Chem. Soc. 133 6720 - 6727    DOI : 10.1021/ja200079a
Scott MG , Yan H , Hancock RE 1999 Biological properties of structurally related alpha-helical cationic antimicrobial peptides. Infect. Immun. 67 2005 - 2009
Shai Y 2002 Mode of action of membrane active antimicrobial peptides. Biopolymers 66 236 - 249    DOI : 10.1002/bip.10260
Shin SY , Lee MK , Kim KL , Hahm KS 1997 Structure-antitumor and hemolytic activity relationships of synthetic peptides derived from cecropin A-magainin 2 and cecropin A-melittin hybrid peptides. J. Pept. Res. 50 279 - 285    DOI : 10.1111/j.1399-3011.1997.tb01469.x
Steiner H , Andreu D , Merrifield RB 1988 Binding and action of cecropin and cecropin analogues: antibacterial peptides from insects. Biochim. Biophys. Acta 939 260 - 266    DOI : 10.1016/0005-2736(88)90069-7
Yang L , Harroun TA , Weiss TM , Ding L , Huang HW 2001 Barrel-stave model or toroidal model? A case study on melittin pores. Biophys. J. 81 1475 - 1485    DOI : 10.1016/S0006-3495(01)75802-X
Zasloff M 1987 Magainins, a class of antimicrobial peptides fromXenopusskin: isolation, characterization of two active forms, and partial cDNA sequence of a precursor. Proc. Natl. Acad. Sci. USA 84 5449 - 5453    DOI : 10.1073/pnas.84.15.5449
2002 Antimicrobial peptides of multicellular organisms. Nature 415 389 - 395    DOI : 10.1038/415389a
Zhu WL , Song YM , Park Y , Park TH , Yang ST , Kim JI 2007 Substitution of the leucine zipper sequence in melittin with peptoid residues affects self-association, cell selectivity, and mode of action. Biochim. Biophys. Acta Biomembr. 1768 1506 - 1517    DOI : 10.1016/j.bbamem.2007.03.010