In this report, we present studies on the large conductance mechanosensitive ion channel (MscL) from E. coli in detergent micelles and lipid vesicle. Both transmission Fourier transform infrared spectroscopy and circular dichroism (CD) spectra indicate that the protein is highly helical in detergent as well as liposomes. The secondary structure of the proteins was shown to be highly resistant towards denaturation (25-95°C) based on an ellipticity thermal profile. Amide H+/D+ exchange was shown to be extensive (ca. 66%), implying that two thirds of the protein are water accessible. MscL, reconstituted in oriental lipid bilayers, was shown to possess a net bilayer orientation using dichroic ratios measured by attenuated total- reflection Fourier transform infrared spectroscopy. Here, we present and discuss this initial set of structural data on this new family of ion- channel proteins.
Bibliographical noteFunding Information:
This work was funded in part by a grant to Axel T. Briinger from NIH (GM-54160-01) and a grant to Sergei Sukharev from NASA (NAGW-4934).
- Circular dichroism
- Fourier transform infrared spectroscopy (FT-IR)
- Ion channel
- Lipid bilayer
- Membrane protein