This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services E-mail this article to a friend Similar articles in this journal Similar articles in ASM journals Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dashper, S. G. Articles by Reynolds, E. C. Search for Related Content PubMed PubMed Citation Articles by Dashper, S. G. Articles by Reynolds, E. C.

 Previous Article  |  Next Article 

Antimicrobial Agents and Chemotherapy, June 2005, p. 2322-2328, Vol. 49, No. 6
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.6.2322-2328.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Divalent Metal Cations Increase the Activity of the Antimicrobial Peptide Kappacin

Stuart G. Dashper, Neil M. O'Brien-Simpson, Keith J. Cross, Rita A. Paolini, Brigitte Hoffmann, Deanne V. Catmull, Marina Malkoski, and Eric C. Reynolds^*

CRC for Oral Health Science, School of Dental Science, University of Melbourne, 711 Elizabeth Street, Melbourne, Victoria 3000, Australia

Received 20 September 2004/ Returned for modification 22 September 2004/ Accepted 30 January 2005

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 Asp¹⁴⁸ to Ala¹⁴⁸ substitution is responsible for the lesser antibacterial activity of -casein-B(106-169). Kappacin was shown to have membranolytic action at concentrations above 30 µM 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 ZnCl₂ reduced bacterial viability by 3 log₁₀ and suppressed recovery of viability. In contrast 20 mM ZnCl₂ alone reduced bacterial viability by 1 log₁₀ followed by rapid recovery. In conclusion, kappacin has a membranolytic, antibacterial effect that is enhanced by the presence of divalent cations.

---

* Corresponding author. Mailing address: CRC for Oral Health Science, School of Dental Science, University of Melbourne, 711 Elizabeth Street, Melbourne, Victoria 3000, Australia. Phone: 61 3 9341 0270. Fax: 61 3 9341 0236. E-mail: e.reynolds{at}unimelb.edu.au.

---

Antimicrobial Agents and Chemotherapy, June 2005, p. 2322-2328, Vol. 49, No. 6
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.6.2322-2328.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Wang, M., Liu, L.-H., Wang, S., Li, X., Lu, X., Gupta, D., Dziarski, R. (2007). Human Peptidoglycan Recognition Proteins Require Zinc to Kill Both Gram-Positive and Gram-Negative Bacteria and Are Synergistic with Antibacterial Peptides. J. Immunol. 178: 3116-3125 [Abstract] [Full Text]