Naja naja atra Cardiotoxins (CTXs), basic polypeptides of 60 amino acid residues adopt a three-fingered loop-folding topology and show cytotoxicity for human tissues in targeting cell membrane. Despite having highly similar sequence, the six CTX isoforms also display different cytotoxic potencies and hemolytic activities. The goal of these studies is to explore the mechanical processes that involved in membrane-damaging activities of CTXs on vesicles composed of different cell membrane components, and to delineate the events that lead to different biological activities of CTXs. The studies were performed by estimating the color transformation of phospholipid/polydiacetylene vesicles and the fluorescence enhancement of fluorescein-labeled phospholipid/protein or fluorescein released from vesicles. It was found that vesicles consisted of unsaturated phospholipids improve membrane-damaging activity of CTXs and adopt a vital membrane-bound conformation of CTXs. In contract, the characteristic of vesicles consisted of saturated phospholipids was against CTXs adopting an essential membrane-damaging structure. It was also found that not only electrostatic force but also hydrophobic force were involved in the interaction between CTXs and membrane. Comparing with phosphatidylcholine-only vesicles, CTXs displayed higher membrane-damaging activity for the sphingomyelin-containing vesicles, and the loop2 region of CTXs play a crucial role for the membrane-damaging activity of sphingomyelin-containing vesicles. Besides, the CTX3 and CTX5 would interact with the H-antigen of blood group O red blood cells, but only the binding of CTX3 with H-antigen reduce its membrane-damaging activity for red blood cells membrane. Moreover, the fusogenicity of CTXs is responsible for the membrane-damaging activity of CTXs toward bacterial membrane-mimicking vesicles. The cardiolipin have the potency to improve the fusogenicity of CTX3, which induced the bactericidal activity toward the cardiolipin-containing bacterium.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0706112-155756 |
| Date | 06 July 2012 |
| Creators | Kao, Pei-Hsiu |
| Contributors | Chien-Cheng Chen, Kuang-hung Cheng, Shinne-Ren Lin, Chun-Chang Chang, Long-Sen Chang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0706112-155756 |
| Rights | user_define, Copyright information available at source archive |
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