Divalent Metal Cations Increase the Activity of the Antimicrobial Peptide Kappacin

Abstract

Kappacin, nonglycosylated -casein(106-169), is a novel antimicrobial peptide produced from -casein found in bovine milk. There are two major genetic forms of kappacin, A and B, and using synthetic peptides corresponding to the active region, -casein(138-158), of these forms, we have shown that the Asp 148 to Ala 148 substitution is responsible for the lesser antibacterial activity of -casein-B(106-169). Kappacin was shown to have membranolytic action at concentrations above 30 M at acidic pH when tested against artificial liposomes. There was little membranolytic activity at neutral pH, which is consistent with the lack of antibacterial activity of kappacin against Streptococcus mutans at this pH. Kappacin specifically bound two zinc or calcium ions per mol, and this binding enhanced antibacterial activity at neutral pH. Nuclear magnetic resonance analysis indicated that a -casein-A(138-158) synthetic peptide undergoes a conformational change in the presence of the membrane solvent trifluoroethanol and excess divalent metal ions. This change in conformation is presumably responsible for the increase in antibacterial activity of kappacin detected in the presence of excess zinc or calcium ions at neutral pH. When tested against the oral bacterial pathogen S. mutans cultured as a biofilm in a constant-depth film fermentor, a preparation of 10 g/liter kappacin and 20 mM ZnCl 2 reduced bacterial viability by 3 log 10 and suppressed recovery of viability. In contrast 20 mM ZnCl 2 alone reduced bacterial viability by Ϸ1 log 10 followed by rapid recovery. In conclusion, kappacin has a membranolytic, antibacterial effect that is enhanced by the presence of divalent cations.

Comparative functional properties of engineered cationic antimicrobial peptides consisting exclusively of tryptophan and either lysine or arginine

“…These cations also interact with proteoglycan and wall teichoic/lipoteichoic acids of Gram-positive bacteria (Swoboda et al, 2010;Thomas & Rice, 2014), a process targeted by the anionic antibiotic daptomycin (Straus & Hancock, 2006). Conversely, the activity of cationic AMPs tends to be inhibited by divalent cations (Dashper et al, 2005;Zhang et al, 2005;Sugiarto & Yu, 2007), and the strength of that inhibition may vary with the test peptide and type of (Gram-positive or Gram-negative) organisms as supported by the data. Because of the presence of Ca 2+ and Mg 2+ in biological matrices (e.g.…”

“…AMPs are ubiquitous effector peptides with amphipathic (usually cationic) structures representing the first line of defence against infectious pathogens (Hancock, 2001;Hancock et al, 2006). As an essential component of innate immunity, AMPs provide host epithelial surfaces and neutrophils with effective microbial killing mechanisms that are rapid and independent of the reactive oxygen species (Dashper et al, 2005) antimicrobial pathway Peschel & Sahl, 2006;Hell et al, 2010). While several bactericidal mechanisms have been identified among diverse structural classes, cationic AMPs typically recognize their microbial target by electrostatic interactions between their highly electropositive hydrophilic peptide motif and the electronegative lipids [e.g.…”

Oxantel Disrupts Polymicrobial Biofilm Development of Periodontal Pathogens

“…Cell density was monitored over a period of 110 h by measuring the absorbance of the culture at 650 nm (A 650 ) using a UV-visible spectrophotometer (Varian). The MIC was calculated by linear regression of the growth data after 50 h of incubation with increasing concentrations of the inhibitor (39).…”

Diet Intake and Caries Prevalence in Four-Year-Old Children Living in a Low-Prevalence Country

“…Caseinophosphopeptide, derived from ␤ -casein, increases calcium levels at the tooth interface and reduces caries in situ Reynolds et al, 2003] and in vivo [Hay and Thomson, 2002]. The caseinoglycomacropeptide and kappacin, derived from -casein, inhibit adhesion and metabolism of mutans streptococci, respectively, in vitro [Schüpbach et al, 1996;Guggenheim et al, 1999;Dashper et al, 2005]. Milk and cheese products supplemented with probiotic lactobacilli and products supplemented with xylitol are other examples of foods reported to reduce caries development in vivo [Alanen et al, 2000;Nase et al, 2001].…”