scholarly journals Plasticity of lipid-protein interactions in the function and topogenesis of the membrane protein lactose permease from Escherichia coli

2010 ◽  
Vol 107 (34) ◽  
pp. 15057-15062 ◽  
Author(s):  
M. Bogdanov ◽  
P. Heacock ◽  
Z. Guan ◽  
W. Dowhan
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Protein Interactions ◽  
Lactose Permease ◽  
Lipid Protein Interactions

scholarly journals To flip or not to flip: lipid–protein charge interactions are a determinant of final membrane protein topology

2008 ◽  
Vol 182 (5) ◽  
pp. 925-935 ◽  
Author(s):  
Mikhail Bogdanov ◽  
Jun Xie ◽  
Phil Heacock ◽  
William Dowhan
Keyword(s):  
Protein Interactions ◽  
Transmembrane Domain ◽  
Lactose Permease ◽  
Membrane Bilayer ◽  
Net Charge ◽  
Protein Charge ◽  
Membrane Protein Topology ◽  
Negative Charge Density ◽  
Lipid Protein Interactions ◽  
Molecular Hinge

The molecular details of how lipids influence final topological organization of membrane proteins are not well understood. Here, we present evidence that final topology is influenced by lipid–protein interactions most likely outside of the translocon. The N-terminal half of Escherichia coli lactose permease (LacY) is inverted with respect to the C-terminal half and the membrane bilayer when assembled in mutants lacking phosphatidylethanolamine and containing only negatively charged phospholipids. We demonstrate that inversion is dependent on interactions between the net charge of the cytoplasmic surface of the N-terminal bundle and the negative charge density of the membrane bilayer surface. A transmembrane domain, acting as a molecular hinge between the two halves of the protein, must also exit from the membrane for inversion to occur. Phosphatidylethanolamine dampens the translocation potential of negative residues in favor of the cytoplasmic retention potential of positive residues, thus explaining the dominance of positive over negative amino acids as co- or post-translational topological determinants.

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