Cation鈭捪€ Interactions As Lipid-Specific Anchors for Phosphatidylinositol-Specific Phospholipase C

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• 作者：C茅dric Grauffel ; Boqian Yang ; Tao He ; Mary F. Roberts ; Anne Gershenson ; Nathalie Reuter
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：April 17, 2013
• 年：2013
• 卷：135
• 期：15
• 页码：5740-5750
• 全文大小：419K
• 年卷期：v.135,no.15(April 17, 2013)
• ISSN：1520-5126

文摘

Amphitropic proteins, such as the virulence factor phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis, often depend on lipid-specific recognition of target membranes. However, the recognition mechanisms for zwitterionic lipids, such as phosphatidylcholine, which is enriched in the outer leaflet of eukaryotic cells, are not well understood. A 500 ns long molecular dynamics simulation of PI-PLC at the surface of a lipid bilayer revealed a strikingly high number of interactions between tyrosines at the interfacial binding site and lipid choline groups with structures characteristic of cation鈭捪€ interactions. Membrane affinities of PI-PLC tyrosine variants mostly tracked the simulation results, falling into two classes: (i) those with minor losses in affinity, K_d(mutant)/K_d(wild-type) 鈮?5 and (ii) those where the apparent K_d was 50鈥?00 times higher than wild-type. Estimating 螖螖G for these Tyr/PC interactions from the apparent K_d values reveals that the free energy associated with class I is 1 kcal/mol, comparable to the value predicted by the Wimley鈥揥hite hydrophobicity scale. In contrast, removal of class II tyrosines has a higher energy cost: 2.5 kcal/mol toward pure PC vesicles. These higher energies correlate well with the occupancy of the cation鈭捪€ adducts throughout the MD simulation. Together, these results strongly indicate that PI-PLC interacts with PC headgroups via cation鈭捪€ interactions with tyrosine residues and suggest that cation鈭捪€ interactions at the interface may be a mechanism for specific lipid recognition by amphitropic and membrane proteins.