PROTEIN-INDUCED SURFACE STRUCTURING IN MYELIN MEMBRANE MONOLAYERS
Carla M. Rosetti 1 and Bruno Maggio 2*
1 CIQUIBIC- Depto. Qca. Biológica. Fac. Cs. Qcas. UNC
2 Facultad de Ciencias Quimicas
* To whom correspondence should be addressed. E-mail: bmaggio{at}dqb.fcq.unc.edu.ar.
Submitted on May 14, 2007
Revised on June 24, 2007
Accepted on 13 July 2007
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Abstract |
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Monolayers prepared from myelin conserve all the compositional complexity of the natural membrane when spread at the air-water interface. They show a complex pressure-dependent surface pattern that, on compression, changes from the coexistence of two liquid phases to a viscous fractal phase embedded in a liquid phase. We dissected the role of major myelin protein components, Myelin Basic Protein (MBP) and Folch-Lees Proteolipid protein (PLP) as crucial factors determining the structural dynamics of the interface. By analyzing mixtures of a single protein with the myelin lipids we found that MBP and PLP have different surface pressure dependent behaviors. MBP stabilizes the segregation of two liquid phases at low pressures and becomes excluded from the film under compression, remaining adjacent to the interface. PLP, on the contrary, organizes a fractal-like pattern at all surface pressures when included in a monolayer of the protein-free myelin lipids but it remains mixed in the MBP-induced liquid phase. The resultant surface topography and dynamics is regulated by combined near to equilibrium and out-of-equilibrium effects. PLP appears to act as a surface skeleton for the whole components while MBP couples the structuring to surface pressure dependent extrusion and adsorption processes.
Key Words:
Brewster angle microscopy, fluorescence microscopy, lipid-protein interactions, natural membrane monolayers, segregated domains, surface skeleton
