Lipid membranes protein interaction

Further investigations were carried out at lipid double layers and at phospholipids of membranes. Lipid-lipid and lipid-protein interactions were recognized by diazirine labeling (79PNA2595). 

Baumgartner and coworkers [145,146] study lipid-protein interactions in lipid bilayers. The lipids are modeled as chains of hard spheres with heads tethered to two virtual surfaces, representing the two sides of the bilayer. Within this model, Baumgartner [145] has investigated the influence of membrane curvature on the conformations of a long embedded chain (a protein ). He predicts that the protein spontaneously localizes on the inner side of the membrane, due to the larger fluctuations of lipid density there. Sintes and Baumgartner [146] have calculated the lipid-mediated interactions between cylindrical inclusions ( proteins ). Apart from the... 

Biological membranes fluidity order parameters lipid-protein interactions translational diffusion site accessibility structural changes membrane potentials complexes and binding energy-linked and light-induced changes effects of additives location of proteins lateral organization and dynamics... 

Lipid-protein interactions are of major importance in the structural and dynamic properties of biological membranes. Fluorescent probes can provide much information on these interactions. For example, van Paridon et al.a) used a synthetic derivative of phosphatidylinositol (PI) with a ris-parinaric acid (see formula in Figure 8.4) covalently linked on the sn-2 position for probing phospholipid vesicles and biological membranes. The emission anisotropy decays of this 2-parinaroyl-phosphatidylinositol (PPI) probe incorporated into vesicles consisting of phosphatidylcholine (PC) (with a fraction of 5 mol % of PI) and into acetylcholine receptor rich membranes from Torpedo marmorata are shown in Figure B8.3.1. 

The fluorescence energy transfer process has been widely used to determine the distance between fluorophores, the surface density of fluorophores in the lipid bilayer, and the orientation of membrane protein or protein segments, often with reference to the membrane surface and protein-protein interactions. Membranes are intrinsically dynamic in nature, so that so far the major applications have been the determination of fixed distances between molecules of interest in the membrane. 

B. Hudson and S. A. Cavalier, in Studies ofMembrane Dynamics and Lipid-Protein Interactions with Parinaric Acid in Speclroscopic Membrane Probes Vol. 1 (L. Loew, ed.), CRC Press, Inc., Boca Raton, Florida (1988). 

Rytdmaa, M., and Kinnunen, P.K.J., 1995, ReversibUity of the binding of cytochrome c to Uposomes. Implications for lipid-protein interactions./. B/oZ. Chem., 270 3197-3202 Salamon, Z., and ToUin, G., 1996, Surface plasmon resonance studies of complex formation between cytochrome c and bovine cytochrome c oxidase incorporated into a supported planar Upid bUayer. II. Binding of cytochrome c to oxidase-containing cardiohpin /phosphatidylcholine membranes. Biophys. J., 71 858-867 Salamon, Z., and ToUin, G., 1997, Interaction ofhorse heart cytochrome c with Upid bilayer membranes effects on redox potentials. J. Bioenerg. Biomembr. 29 211-221 Scarlett, J.L., and Murphy, M.P., 1997, Release of apoptogenic proteins from the... 

Lysobisphosphatidic acid (LBPA) also distinguishes late endosomes. LBPA is shaped like an inverted cone it has a much larger head than tail and enters highly curved membrane regions. The lipid may help in the accumulation of molecules like cholesterol by specific lipid-protein interactions (131). 

As a second possibility, lipid-protein interaction must be considered. The red shift might be explained in terms of hydrophobic interaction of the hydrocarbon chains of phospholipids with the protein in such a way that the amide chromophores are transferred to a less polar environment (89). Again, the hypothesis can be tested by removal of lipid. The existence of the red shift in lipid-depleted mitochondria and in lipid-free mitochondrial structural protein shows that lipid-protein interaction is not necessary to produce the ORD spectra characteristic of membranes. It is possible that if some molecular rearrangement occurs during the extraction process, a red shift caused by hydrophobic lipid-protein association could be replaced with a red shift arising from hydrophobic protein-protein association. Such an explanation is unlikely, especially in view of the retention of the unit membrane structure in electron micrographs taken of extracted vesicles (30). On the basis of ORD, then, the most reasonable conclusion is that the red shift need not be assigned to lipid-protein association. 

The present knowledge about molecular organization in lyotropic liquid crystalline phases is summarized. Particular attention is given to biologicaly relevant structures in lipid-water systems and to lipid-protein interactions. "New findings are presented on stable phases (gel type) that have ordered lipid layers and high water content. Furthermore, electrical properties of various lipid structures are discussed. A simple model of l/l noise in nerve membranes is presented as an example of interaction between structural and electrical properties of lipids and lipidr-protein complexes. 

The possibility of obtaining information about lipid-protein interaction makes Raman spectroscopy a useful technique for structural studies of membranes. As an illustration of spectra recorded from biological samples, see the Raman spectrum of a frog sciatic nerve in Figure 11. The C-H stretching vibration region is characteristic of lipid bilayers in a... 

Although numerous models for the structure of membranes have been proposed, the structural features which are generally accepted at present are rather similar to the original Danielli-Davson model. There is convincing evidence that the structure is dominated by lipid bilayers. The state of order of the hydrocarbon chains is now being studied extensively by many groups (see below). Less is known about the proteins. Besides the proteins that are located on the outside according to the Danielli-Davson model, there are also proteins that are partly buried in the hydro-phobic interior of the lipid layer however, little is known about the lipid-protein interaction. 

A similar type of interaction is thought to occur in membrane lipoprotein molecules. The problem in the latter studies is that the membrane apoproteins are not easily solubilized. If further information on the structure of biological membranes is required, then it is recommended that a recent book by Petty (1993) and one edited by Wirtz et al. (1993) be placed on a must reading list. An older, but very good, short review on lipid-protein interaction possibilities in membranes is one presented by Danielli (1982), who is widely recognized as a pioneer as well as a legend in this field. 

Even though our understanding of the possible types of lipid-protein interactions in membranes has developed only recently, it was evident to early investigators that neutral solvents per se were the most effective for isolation purposes. Perhaps the most widely used solvent extraction procedure for many years was that employing a mixture of ethanol-diethyl ether (usually 1 3, v/v). This technique involved extraction of a tissue with this solvent combination for several hours at 55-60°C (Bloor, 1928). However, as more refined techniques were developed for the detection and assay of lipids, it became evident that this solvent (and condition) could have a deleterious... 

Sansom MSP, PJ Bond, SS Deol, A Grottesi, S Haider, ZA Sands (2005) Molecular simulations and lipid-protein interactions potassium channels and other membrane proteins. Biochem. Soc. Trans. 33 916-920... 

Ondrias, K., Stasko, A., Marko, V., and Nosal, R. (1989), Influence of beta-adrenoceptor blocking drugs on lipid-protein interaction in synaptosomal membranes. An ESR study, Chem. Biol. Interact., 69, 87-97. 

McElhaney, R. N. Differential scanning calorimetric studies of lipid-protein interactions in model membrane systems. Biochimica et Biophysica acta 564 361-421, 1986. 

Mouritsen, O. G. and Bloom, M., Models of lipid-protein interactions in membranes. Annual Review of Biophysics and Biomolecular Structure 22 145-171, 1993. 

The classihcation scheme of Papahadjopoulos et al. (32), appropriately modihed for type 3 proteins, is still of some use in studies of lipid-protein interactions, although some proteins, at least under certain conditions, do not fall neatly into any of these three categories. It seems that all naturally occurring membrane proteins studied to date interact with lipid bilayers by both hydrophobic and electrostatic interactions and that different membrane proteins differ only in the specihc types and relative magnitudes of these two general classes of interactions. It is also clear that the behavior exhibited by any particular membrane protein can depend on its conformation, method of reconstitution, and relative concentration, as well as on the polar headgroup and fatty acid composition of the lipid bilayer with which it is interacting (see Reference 17). 

Lee AG. Lipid-protein interactions in biological membranes a structural perspective. Biochim. Biophys. Acta-Biomemb. 2003 1612 1-40. 

Generally speaking, two principal mechanisms operate in the biology of membrane processes, such as membrane transport and permeation. One involves a network of active sites and operates by metabolic energy, and it is referred to as active another is directed by passive diffusion, and it is called passive. This passive mechanism is determined by various aspects of lipid dynamics and lipid-protein interactions, and it can be described in quantitative terms of chemical and phase equilibrium and molecular physics. However, in the highly anisotropic... 

Gonen T, Cheng Y, Sliz P, Hiroaki Y, Fujiyoshi Y, Harrison SC, Walz T. Lipid-protein interactions in double-layered two dimensional crystals of aquaporin-0. Nature 2005 438 633-638. Henderson R, Unwin PN. Three dimensional model of purple membrane obtained by electron microscopy. Nature 1975 257 28-32. 

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