Interactions of α-Lactalbumin and Cytochrome c with Langmuir Monolayers of Glycerophospholipids

Abstract

Interaction of cytochrome c (Cyt c), α-lactalbumin III (α-La III) with Langmuir monolayers of pure and mixed glycerophospholipids was investigated using surface pressure-area (Π-A) isotherms. The general trend was that maximum interaction between protein and phospholipid is observed for mixed (1:1 molar ratio) phospholipid monolayers. Interaction between the protein and the charged phospholipid films was found to be independent of global protein charge. Our data indicate that the proteins interact with the phospholipid films by inserting themselves into the monolayer rather than anchoring to the phospholipid head groups.

Keywords:

• apo alpha-lactalbumin
• cytochrome c
• langmuir monolayer
• lipids
• protein-lipid interactions

Acknowledgements

W. R. G. gratefully acknowledges support from the NFR/NTNU grant 10287305, and Ø.H. acknowledges support from The Norwegian Cancer Society. All the authors thank Professor Aurora Martínez and Professor Holm Holmsen at the Department of Biomedicine, University of Bergen, for helpful discussions.

Notes

^aTaken at the onset of the liquid state using the criterion δΠ/δA ≥ 0.5.

^bCalculated using Equation (1) for Π = 5 mN/m.

^cCalculated using Equation (2) for Π = 5 mN/m.