Interactions of Thionin from Pyrularia pubera with Dipalmitoylphosphatidylglycerol Large Unilamellar Vesicles
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- 作者：Wenhao Huang ; Leo P. Vernon ; Lee D. Hansen ; and John D. Bell
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：March 11, 1997
- 年：1997
- 卷：36
- 期：10
- 页码：2860 - 2866
- 全文大小：159K
- 年卷期：v.36,no.10(March 11, 1997)
- ISSN：1520-4995
文摘
The peptide toxin thionin from Pyrulariapubera binds to dipalmitoylphosphatidylglycerol(DPPG) large unilamellar vesicles as shown by an increase in theintensity and blue-shift of the fluorescenceemission spectrum of the single tryptophan residue of the protein.The magnitude of these fluorescencechanges increased with temperature near the thermotropic phasetransition of DPPG (about 40 
C).Fluorescent probes sensitive to the structure and dynamics of themembrane were used to assess theeffect of thionin binding on bilayer properties. The fluorescenceemission spectra of Prodan, Patman,and Laurdan all showed spectral changes consistent with an increase inbilayer polarity at temperaturesbelow the DPPG phase transition but a decrease in polarity at highertemperatures. Fluorescencepolarization experiments and the ratio of monomer-to-excimerfluorescence of the probe 1,3-bis(1-pyrene)propane suggested that thionin increases the bilayer order above thetransition temperature. Differentialscanning calorimetry revealed that thionin broadens the transition andeither increases or decreases themelting temperature depending on the concentration of the peptide.Taken together, the data are consistentwith at least three distinct interactions of thionin with thebilayer: (1) thionin bound electrostatically tothe bilayer surface; (2) tryptophan of the bound thionin inserted intothe bilayer; (3) high-order aggregatesof thionin-bound vesicles.
C).Fluorescent probes sensitive to the structure and dynamics of themembrane were used to assess theeffect of thionin binding on bilayer properties. The fluorescenceemission spectra of Prodan, Patman,and Laurdan all showed spectral changes consistent with an increase inbilayer polarity at temperaturesbelow the DPPG phase transition but a decrease in polarity at highertemperatures. Fluorescencepolarization experiments and the ratio of monomer-to-excimerfluorescence of the probe 1,3-bis(1-pyrene)propane suggested that thionin increases the bilayer order above thetransition temperature. Differentialscanning calorimetry revealed that thionin broadens the transition andeither increases or decreases themelting temperature depending on the concentration of the peptide.Taken together, the data are consistentwith at least three distinct interactions of thionin with thebilayer: (1) thionin bound electrostatically tothe bilayer surface; (2) tryptophan of the bound thionin inserted intothe bilayer; (3) high-order aggregatesof thionin-bound vesicles.