title: Membrane-bound conformation of Naja nigricollis toxin gamma affects its membrane-damaging activity.
abstract: To address whether the conformational events associated with the absorption of Naja nigricollis toxin gamma on water-lipid interface plays a vital role in its membrane-damaging activity, the present study is carried out. Membrane-damaging activity of toxin gamma on 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC)/1, 2-dimyristoyl-phosphatidic acid (DMPA) vesicles was approximately 13-fold of that on 1, 2-dipalmitoyl-phosphatidylcholine (DPPC)/DMPA vesicles, while the binding affinity of toxin gamma for POPC/DMPA was twofold of that for DPPC/DMPA. Time-resolved fluorescence, acrylamide quenching and Fourier transform infrared spectra showed that POPC/DMPA-bound toxin gamma and DPPC/DMPA-bound toxin gamma did not adopt the same conformation. Moreover, geometrical arrangement of toxin gamma in contact with POPC/DMPA vesicles was different from that with DPPC/DMPA vesicles as evidenced by N-(fluorescein-5-thiocarbamoyl)-1,2-dihexadecanoyl-phosphatidylcholine fluorescence enhancement and cross-linking of membrane-bound toxin gamma. Taken together, our data show that different membrane packing densities arising from phospholipid acyl chain affect membrane-bound conformation of toxin gamma, thus changing its membrane-damaging activity.
authors.affiliation: Institute of Biomedical Sciences, National Sun Yat-Sen University-Kaohsiung Medical University Joint Research Center, National Sun Yat-Sen University, No 70, Lien-Hai Road, Kaohsiung 804, Taiwan, ROC.
authors.forename: Pei-Hsiu
authors.initials: PH
authors.lastname: Kao
authors.forename: Ming-Jung
authors.initials: MJ
authors.lastname: Wu
authors.forename: Long-Sen
authors.initials: LS
authors.lastname: Chang
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects*; D004546:Elapid Venoms / Q000235:genetics* / Q000633:toxicity; D005453:Fluorescence; D008823:Micelles; D010713:Phosphatidylcholines / Q000378:metabolism; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D004546:Elapid Venoms; D008823:Micelles; D010713:Phosphatidylcholines; C028694:1-palmitoyl-2-oleoylphosphatidylcholine