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The effect of hemifluorinated compounds like HF-TAC on solution properties and membrane interaction of the diphtheria toxin T-domain, which inserts into membrane under mildly acidic conditions, is examined to test the ability of HF-TAC to assist proper membrane insertion of proteins. The results show that hemifluorinated surfactants stabilize the low-pH conformation of the T-domain as a water-soluble monomer while acting as low-molecular weight chaperones for its insertion into preformed lipid bilayers.

Research has been conducted on cytochrome b (sub)6 f complexes containing chlorophyll molecule a which can be exchanged for extraneous chlorophyll during purified complex incubation in detergent solution. The study of the site specificity and its location in the complex have been investigated via the use of circular dichroism spectroscopy and photochemical couplings, and the details are reported.

The development of a generic protocol to fold four class A G protein-coupled receptors (GPCRs), which regulate numerous physiological functions to their functional state based on the binding of their respective ligands is presented. The newly developed strategy have potential to be generalized to a large number of GPCRs and study the three-dimensional structure in an environment that bears no similarity, beyond the amphiphilic character, to lipid bilayers.

Some properties of membrane protein/amphipol complexes, which are relevant to their use in membrane protein biochemical and biophysical studies, are discussed.

Amphipathic polymer, amphipol A8-35, is used as a novel environment that allows both [beta]-barrel and [alpha]-helical membrane proteins to fold to their native state, in the absence of detergents or lipids. The feasibility of the method is shown using as models OmpA and FomA, two outer membrane proteins from the eubacteria Escherichia coli and Fusobacterium nucleatum, respectively, and bacteriorhodopsin, a light-driven proton pump from the plasma membrane of the archaebacterium Halobacterium salinarium.

A study was conducted to investigate the sarcoplasmic reticulum Ca(super 2+)-ATPase (SERCA1a) using a set of four amphipols with different chemical structures. The results revealed that as the calcium dissociation involves the opening up of the bundle of transmembrane ATPase segments, the slowing of the process might indicate that multipoint attachment of the polymers to the hydrophobic transmembrane surface damps proteins dynamics.

Which properties of the membrane environment are essential for the folding and oligomerization of transmembrane proteins? Because the lipids that surround membrane proteins in situ spontaneously organize into bilayers, it may seem intuitive that interactions with the bilayer provide both hydrophobic and topological constraints that help the protein to achieve a stable and functional three-dimensional structure. However, one may wonder whether folding is actually driven by the membrane environment or whether the folded state just reflects an adaptation of integral proteins to the medium in which they function. Also, apart from the overall transmembrane orientation, might the asymmetry inherent in biosynthesis processes cause proteins to fold to out-of-equilibrium, metastable topologies? Which of the features of a bilayer are essential for membrane protein folding, and which are not? To which extent do translocons dictate transmembrane topologies? Recent data show that many membrane proteins fold and oligomerize very efficiently in media that bear little similarity to a membrane, casting doubt on the essentiality of many bilayer constraints. In the following discussion, we argue that some of the features of bilayers may contribute to protein folding, stability and regulation, but they are not required for the basic three-dimensional structure to be achieved. This idea, if correct, would imply that evolution has steered membrane proteins toward an accommodation to biosynthetic pathways and a good fit into their environment, but that their folding is not driven by the latter or dictated by insertion apparatuses. In other words, the three-dimensional structure of membrane proteins is essentially determined by intramolecular interactions and not by bilayer constraints and insertion pathways. Implications are discussed. [ABSTRACT FROM AUTHOR]