Possible Role of a PXXP Central Hinge in the Antibacterial Activity and Membrane Interaction of PMAP-23, a Member of Cathelicidin Family
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- 作者：Sung-Tae Yang ; Jae-Hyuck Jeon ; Yangmee Kim ; Song Yub Shin ; Kyung-Soo Hahm ; and Jae Il Kim
- 刊名：Biochemistry
- 出版年：2006
- 出版时间：February 14, 2006
- 年：2006
- 卷：45
- 期：6
- 页码：1775 - 1784
- 全文大小：237K
- 年卷期：v.45,no.6(February 14, 2006)
- ISSN：1520-4995
文摘
Cathelicidins are essential components of the innate immune system of mammals, providingthem a weapon against microbial invasion. PMAP-23 adopting a helix-hinge-helix structure with acentral PXXP motif is a member of the cathelicidin family and has potent killing activities against abroad spectrum of microbial organisms. Although the antimicrobial effect of PMAP-23 is believed to bemediated by membrane disruption, many details of this event remain unclear. Here, we try to characterizethe interaction between PMAP-23 and membrane phospholipids, focusing on the function of the centralPXXP motif. PMAP-PA, in which the Pro residues were substituted by Ala, had significantly more 
-helicalcontent than PMAP-23, but was less amphipathic and more damaging to human erythrocytes andzwitterionic liposomes. The observed differences in the structures and biological activities of PMAP-23and PMAP-PA confirmed the functional importance of the central hinge PXXP motif, which enablesPMAP-23 to adopt a well-defined amphipathic conformation along its entire length and to have selectiveantimicrobial activity. CD and Trp fluorescence studies using fragments corresponding to the two helicalhalves of PMAP-23 revealed that the N-terminal half binds to anionic phospholipids and is more stablethan the C-terminal half. In addition, Trp fluorescence quench analyses revealed that the C-terminal helixinserts more deeply into the hydrophobic region of the membrane than the N-terminal helix. Finally,observations made using biosensor technology enabled us to distinguish between the membrane bindingand insertion steps, substantiating a proposed kinetic mode of the peptide-membrane interaction in whichPMAP-23 first attaches to the membrane via the N-terminal amphipathic helix, after which bending and/or swiveling of the PXXP motif enables insertion of the C-terminal helix into the lipid bilayer.
-helicalcontent than PMAP-23, but was less amphipathic and more damaging to human erythrocytes andzwitterionic liposomes. The observed differences in the structures and biological activities of PMAP-23and PMAP-PA confirmed the functional importance of the central hinge PXXP motif, which enablesPMAP-23 to adopt a well-defined amphipathic conformation along its entire length and to have selectiveantimicrobial activity. CD and Trp fluorescence studies using fragments corresponding to the two helicalhalves of PMAP-23 revealed that the N-terminal half binds to anionic phospholipids and is more stablethan the C-terminal half. In addition, Trp fluorescence quench analyses revealed that the C-terminal helixinserts more deeply into the hydrophobic region of the membrane than the N-terminal helix. Finally,observations made using biosensor technology enabled us to distinguish between the membrane bindingand insertion steps, substantiating a proposed kinetic mode of the peptide-membrane interaction in whichPMAP-23 first attaches to the membrane via the N-terminal amphipathic helix, after which bending and/or swiveling of the PXXP motif enables insertion of the C-terminal helix into the lipid bilayer.