Polypeptide insertion into lipid bilayer

Immunoc3d ochemical and ELISA studies showed that all N- and C-terminal receptor fragments capable of forming functional receptor complexes in the cotransfection experiments (see above) were stably inserted into lipid bilayers, even when expressed alone. Similar to the wild type m3 mAChR, the various receptor polypeptides were found both intraceUularly (ER/Golgi complex) as well as in the plasma membrane [20]. These observations suggest that the presence of the full-length receptor protein is not essential for membrane insertion and proper intracellular trafficking. 

Relaxation-related work on proteins and polypeptides makes typically use of H, and NMR. A couple of papers have dealt with measurements on in fluorine-labelled aminoacids incorporated into peptide stuctures. Shi and co-workers introduced, at some specific sites, an unnatural fluorine-containing aminoacid and a nitroxide spin-label into a multidomain protein known to exist in different conformations. Measurements of F PRE allowed to determine the conformation under different conditions. Suzuki et used another fluorine-containing amino acid, inserted into different parts of a membrane-active peptide, as a local dynamics probe. They measured F transverse relaxation to examine changes in the mobility in different regions of the peptide upon binding to a lipid bilayer. 

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