PMID: 40598Nov 2, 1979

Cooperative lipid-protein interaction. Effect of pH and ionic strength on polymyxin binding to phosphatidic acid membranes

Biochimica Et Biophysica Acta
F Sixl, H J Galla


The binding of polymyxin-B to charged dipalmitoyl phosphatidic acid membranes has been studied as function of the external pH and of the ionic strength of the buffer solution. The phase transition curves were obtained by measuring the fluorescence depolarization of diphenyl hexatriene incorporated into the membrane with temperature. The molecular process of polymyxin binding was elucidated: 1. At an ionic strength of I greater than or equal to 0.1 mol/l a three step phase transition curve is found. A high-temperature step corresponds to the non-bound lipid. A lowered phase transition concerns to protein-bound lipid domains. This again is splitted into two steps. An inner core of the domain is characterized by a lipid-protein complex which is stabilized through hydrophobic and electrostatic interactions between polymyxin and the charged lipid. This core is surrounded by an outer belt of only hydrophobically bound molecules. This part shows a lower phase transition temperature than the inner core. 2. The binding curves of polymyxin to phosphatidic acid membranes depend strongly on the ionic strength of the water phase. The cooperativity of the binding process increases with increasing ionic strength and reaches a constant value a...Continue Reading


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Related Concepts

Tissue Membrane
Dipalmitoylphosphatidic acid
Plasma Protein Binding Capacity
Protein Complex Location
Protein-Protein Interaction
Phosphatidic Acid
Diphenyl (fungicide)

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