Protein-mediated surface structuring in biomembranes

Abstract

The lipids and proteins of biomembranes exhibit highly dissimilar conformations, geometrical shapes, amphipathicity, and thermodynamic properties which constrain their two-dimensional molecular packing, electrostatics, and interaction preferences. This causes inevitable development of large local tensions that frequently relax into phase or compositional immiscibility along lateral and transverse planes of the membrane. On the other hand, these effects constitute the very codes that mediate molecular and structural changes determining and controlling the possibilities for enzymatic activity, apposition and recombination in biomembranes. The presence of proteins constitutes a major perturbing factor for the membrane sculpturing both in terms of its surface topography and dynamics. We will focus on some results from our group within this context and summarize some recent evidence for the active involvement of extrinsic (myelin basic protein), integral (Folch-Lees proteolipid protein) and amphitropic (cFos and c-Jun) proteins, as well as a membrane-active amphitropic phosphohydrolytic enzyme (neutral sphingomyelinase), in the process of lateral segregation and dynamics of phase domains, sculpturing of the surface topography, and the bi-directional modulation of the membrane biochemical reactivity.

White Matter Rafting––Membrane Microdomains in Myelin

“…Although still unresolved, rafts may be involved in membrane trafficking [121,135,136] and growth factor signalling [97, 137,138] in OLs. In these putative signalling platforms, classic MBP may facilitate the relay of signals from the plasma membrane to the cell interior [89, 126,132,139], perhaps indirectly by modulating the local physicochemical properties of the membrane [24,127,140,141] and of the underlying cytoskeleton [142][143][144][145][146]. It is known that there is an altered distribution of post-translationally modified components of MBP in MS [128,147].…”

“…thus remains an open one [126,127,132,192]. The various posttranslational modifications of MBP may serve to target it and modulate its interaction with the myelin membrane, so as to define microdomains with specific physicochemical properties [24,127,132,140,141].…”

Composition-driven Surface Domain Structuring Mediated by Sphingolipids and Membrane-active Proteins

“…It is interesting that the protein-free phospholipid domains having compositionally-independent melting show marked changes of their thermodynamically-correlated cluster sizes and distribution functions in the presence of the protein. This clearly points out the existence of a so far disregarded structural influence on a long-range scale among the coexisting phase domains on the thermodynamic level [168].…”

“…By contrast the increase of transition enthalpy, with a slight increase of transition temperature, induced by MBP on the thermotropic behavior of gangliosides corresponds to a surface-mediated protein adsorption [166,167]. Statistical thermodynamic analysis of the phase transition process [168] revealed that increasing proportions of MBP induces large and broadly distributed glycosphingolipid-enriched clusters (in terms of the number of thermodynamicallycorrelated molecules) of the higher melting domains. On the other hand, in the presence of MBP, the segregated low-temperature (pure or highly phospholipid-enriched) domains become quite small and rather narrowly distributed.…”

Efeito de materiais particulados em sistemas modelos de biomembranas

“…The study allowed concluding that PM originate from burned sugar cane leaves has an effect over some features of PS model systems and those properties have the potential to interfere in the perfect performance of these systems in biological environments. (Wiecek et al, 2008;Maggio et al, 2005;Gidalevitz et al, 2003;Lourenzoni et al, 2007). Inclusive em nosso grupo de pesquisa, tem-se demonstrado a utilidade dessa ferramenta na investigação da interação entre fosfolipídios com:…”