Effect of pH on the Pore Forming Activity and Conformational Stability of Ostreolysin, a Lipid Raft-Binding Protein from the Edible Mushroom Pleurotus ostreatus
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- 作者：Sabina Berne ; Kristina Sep
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- 刊名：Biochemistry
- 出版年：2005
- 出版时间：August 23, 2005
- 年：2005
- 卷：44
- 期：33
- 页码：11137 - 11147
- 全文大小：416K
- 年卷期：v.44,no.33(August 23, 2005)
- ISSN：1520-4995
文摘
Ostreolysin, a pore-forming protein from the edible oyster mushroom (Pleurotus ostreatus),is a member of the aegerolysin protein family, a novel group of small acidic proteins found in bacteria,molds, mushrooms, and plants. It binds to lipid rafts and interacts specifically with cholesterol-rich lipiddomains. In this study, ostreolysin was classified as a single-domain all-
-structured protein on the basisof cDNA sequencing. pH-induced and thermally induced unfolding of ostreolysin was studied by meansof CD, UV absorption, and intrinsic tryptophan fluorescence to characterize conformational transitionsassociated with its functional properties, i.e., binding to lipid membranes, pore forming activity on lipidvesicles, and hemolysis. At 25 
C and between pH 6 and 9, ostreolysin adopted a monomeric andthermodynamically stable nativelike conformation, characterized by rigid tertiary structure and predominantly -sheet secondary structure. Between pH 2 and 3, the protein underwent an irreversible transitionto a partially unfolded, molten globule-like state which bound ANS, and exhibited disrupted tertiary structureand enhanced non-native 
-helical structure. Functional studies showed that, unlike colicins and someother bacterial pore-forming toxins, the acid-induced molten globule-like state of ostreolysin is not relevantfor lipid binding and pore formation. Instead, the compact native state was necessary for binding tocholesterol/sphingomyelin multilamellar vesicles, optimally in the pH range from 6 to 7, and for poreformation and hemolysis, maximally between pH 7 and 8.
-structured protein on the basisof cDNA sequencing. pH-induced and thermally induced unfolding of ostreolysin was studied by meansof CD, UV absorption, and intrinsic tryptophan fluorescence to characterize conformational transitionsassociated with its functional properties, i.e., binding to lipid membranes, pore forming activity on lipidvesicles, and hemolysis. At 25 C and between pH 6 and 9, ostreolysin adopted a monomeric andthermodynamically stable nativelike conformation, characterized by rigid tertiary structure and predominantly -sheet secondary structure. Between pH 2 and 3, the protein underwent an irreversible transitionto a partially unfolded, molten globule-like state which bound ANS, and exhibited disrupted tertiary structureand enhanced non-native -helical structure. Functional studies showed that, unlike colicins and someother bacterial pore-forming toxins, the acid-induced molten globule-like state of ostreolysin is not relevantfor lipid binding and pore formation. Instead, the compact native state was necessary for binding tocholesterol/sphingomyelin multilamellar vesicles, optimally in the pH range from 6 to 7, and for poreformation and hemolysis, maximally between pH 7 and 8.