A Bactericidal Cecropin-A Peptide with a Stabilized α-Helical Structure Possess an Increased Killing Capacity But No Proinflammatory Activity

Author: Fu Huamei   Björstad Åse   Dahlgren Claes   Bylund Johan  

Publisher: Springer Publishing Company

ISSN: 0360-3997

Source: Inflammation, Vol.28, Iss.6, 2004-12, pp. : 337-343

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Abstract

Antibacterial peptides are part of the innate immune system in a variety of different species including humans. Some of these peptides have also been shown to have effects on immune competent cells such as professional phagocytes. We have recently shown that a cecropin-like peptide from Helicobacter pylori, Hp(2–20), in addition to being bactericidal possesses proinflammatory effects and can recruit and activate neutrophils as well as monocytes. It is well established that cecropins have the ability to adopt amphipathic α-helices, which is thought to be required for their bactericidal activity. In this study we show the same structural requirements for Hp(2–20). Breaking the helical structure of Hp(2–20) reduced the antibacterial effect and abolished its proinflammatory activity. A C-terminal truncated cecropin A peptide that highly resembles Hp(2–20) failed to activate neutrophils and computer-based structural simulations revealed a difference between the two peptides in the stability of their helical structures. A hybrid peptide with amino acid substitutions stabilizing the α-helical structure of the truncated cecropin A peptide did not introduce any proinflammatory activity; the bactericidal activity was, however, increased. We thus conclude that the proinflammatory effect of Hp(2–20) is a unique sequence-specific feature of the peptide and the ability to adopt a stable amphipathic helix is a necessary but not sufficient criterion for the functional dualism of the peptide.

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