Membrane mimetic environments alter the conformation of the outer membrane protein BtuB.
Membrane mimetic environments formed from detergents or short-chain phospholipids are widely utilized in structural studies of membrane proteins. Using site-directed spin labeling (SDSL), we show that micelle and isotropic bicellar environments alter the N-terminal region of BtuB, the outer membrane vitamin B12 transporter found in Escherichia coli. These membrane mimetic systems promote an unfolding of the N-terminus of the protein that does not occur when the protein is in either native or reconstituted bilayers. The N-terminal Ton box of BtuB has been shown to exist in two conformations, depending upon the presence or absence of substrate. However, the detergent-destabilized conformation is different from either the substrate-free or the substrate-bound form of this transporter. This example demonstrates that membrane mimetic systems will not always substitute for the lamellar bilayer environment provided by a biological membrane.
Fanucci
Gail E
GE
Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, VA 22904-4319, USA.
Lee
Jae Y
JY
Cafiso
David S
DS
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D003902:Detergents / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D026901:Membrane Transport Proteins; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry; D011487:Protein Conformation; D018000:Receptors, Peptide / Q000737:chemistry*
D001425:Bacterial Outer Membrane Proteins; C044592:BtuB protein, E coli; D003902:Detergents; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D026901:Membrane Transport Proteins; D010713:Phosphatidylcholines; D018000:Receptors, Peptide; C028694:1-palmitoyl-2-oleoylphosphatidylcholine