Magnetically aligned membrane mimetics enabling comparable chiroptical and magnetic resonance spectroscopy studies.

Lipidic bicelles have been widely used for the analysis of integral membrane proteins where their spontaneous alignment in an magnetic field has been exploited for oriented sample solid-state NMR studies. Many of their physical properties however make them well suited to the analysis of membrane proteins by circular dichroism (CD) and synchrotron radiation circular dichroism (SRCD). In this paper we have identified bicelle compositions that permit comparable studies of integral membrane proteins by solid-state NMR, CD, and SRCD; complementary methods that can provide insights into protein structure and the interactions with drugs and other small molecules.

Relevance of CARC and CRAC Cholesterol-Recognition Motifs in the Nicotinic Acetylcholine Receptor and Other Membrane-Bound Receptors.

Cholesterol is a ubiquitous neutral lipid, which finely tunes the activity of a wide range of membrane proteins, including neurotransmitter and hormone receptors and ion channels. Given the scarcity of available X-ray crystallographic structures and the even fewer in which cholesterol sites have been directly visualized, application of in silico computational methods remains a valid alternative for the detection and thermodynamic characterization of cholesterol-specific sites in functionally important membrane proteins. The membrane-embedded segments of the paradigm neurotransmitter receptor for acetylcholine display a series of cholesterol consensus domains (which we have coined "CARC").

A mirror code for protein-cholesterol interactions in the two leaflets of biological membranes.

Cholesterol controls the activity of a wide range of membrane receptors through specific interactions and identifying cholesterol recognition motifs is therefore critical for understanding signaling receptor function. The membrane-spanning domains of the paradigm neurotransmitter receptor for acetylcholine (AChR) display a series of cholesterol consensus domains (referred to as "CARC"). Here we use a combination of molecular modeling, lipid monolayer/mutational approaches and NMR spectroscopy to study the binding of cholesterol to a synthetic CARC peptide.