Membrane proteins functions

To date, the lipids so far used have been mainly extracts from natural sources such as EPC and archaeal lipids[17,18] The chemical stability of EPC, however, is not sufficient and the membrane permeability to H1 is sometimes too high for quantitative analyses of membrane protein functions. Though archaeal lipids display many preferable features for... 

Amphiphilic compounds are also known as potent modifiers of the bilayer intrinsic radius of curvature and utilize this property to act as a non-specific perturbator of membrane protein function [27]. Catamphiphilic drugs that can interact with the head groups or with the scramblases or flippases can change cell functioning. 

Murphy, M.G., Dietary fatty acids and membrane protein function, J. Nutr. Biochem., 1, 68, 1990. 

Litman, B., and D. Mitchell (1996). A role for phospholipid polyunsaturation in modulating membrane protein function. Lipids S193-S197. 

Andersen OS, Koeppe RE. Bilayer thickness and membrane protein function an energetic perspective. Annu. Rev. Biophys. Biomol. Struct. 2007 36 107-130. 

The lipid bilayer is not passive in determining membrane protein activity and function, and an accumulating body of evidence indicates that there is a coupling of membrane proteins to lipid bilayer properties. These properties include the effect of bilayer curvature strain (20), the role of specific lipids such as phosphoinositides, (21) and the effect of thickness on membrane protein function (22). The lipid composition, as well as the bilayer properties that result from this composition, act as allosteric regulators of membrane protein function. 

The idea of using polymer-supported bilayers has been around for more than a decade (34), but it became practical for chemical and biological applications only more recently. Early versions have used relatively short tethers to link the membranes to the solid substrate and thereby increase their durability for practical applications (25, 35). Because these approaches do not increase the gap distance between substrate and membrane and therefore have not been used to reconstitute integral membrane proteins functionally, they will not be discussed here. 

Lundbaek JA. Regulation of membrane protein function by lipid 31. bilayer elasticity — a single molecule technology to measure the bilayer properties experienced by an embedded protein. J. Phys. Condens. Matter 2006 18 1305-1344. 

The retinal proteins of halobacteria constitute a unique set of light energy transduction devices, based on similar chemistry but designed to perform different functions. The contributions of bacteriorhodopsin to our understanding of the structure and function of membrane proteins have been, and will no doubt continue to be, spectacular. As descriptions of the properties of the other two halobacterial retinal pigments are now becoming available, they promise to provide further insights into how membrane proteins function. 

Numerous studies have been published describing modulation of membrane protein function by changes in the degree of unsaturation of the phospholipid acyl chains. It is... 

This is the mechanism proposed by Datyner to account for CTAC antibacterial, and antifungal to a lesser extent, activity he reports [20]. Martins et al. invoke the ability of the surfactant to disrupt the cell membrane and form mixed micelles with its lipids to account for CTAB and SLS antibacterial activity [29], In contrast, the bacteria-killing efficacy of double-chain surfactants such as DHTDMAC is assigned to an alteration of the membrane protein function resulting from the adsorption of vesicles onto the bacterial membrane. This study was carried out under laboratory conditions (very low ionic strength), and the antibacterial efficacy of fabric softeners under realistic use conditions remains highly questionable. 

The effect of hydrogenation on membrane protein function has been examined using the Ca2+ pump of sarcoplasmic reticulum of rabbit hind-leg muscle [36, 37]. Up to 35% of the unsaturated bonds of the membrane lipids could be saturated in the presence of Wilkinson s catalyst. ATPase activity was completely inhibited on adding catalyst but this could be prevented by preserving the catalyst in its hydride form. When the effect of hydrogenation of sarcoplasmic reticulum on calcium pump activity was assayed in buffers saturated with H2, it was found that removal of 25% of cis double bonds did not affect the activity of Ca2+-ATPase. 

Sachs, J. N., 8c Engelman, D. M. (2006). Introduction to the membrane protein reviews The interplay of structure, dynamics, and environment in membrane protein function. Annual Review of Biochemistry, 75, 707-712. 

The study of protein function is increasingly focused on the interactions between protein structure, electrochemical potentials, and molecular motion. For membrane proteins, insertion through a phospholipid bilayer imparts a defined orientation to the protein and a specified relation between the macroscopic electrical field and the axis of the molecule normal to the membrane. These constraints can be exploited to obtain detailed information about membrane protein function and dynamics, particularly for proteins that form aqueous pores through membranes. The ability to record currents that... 

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