Deuterium/hydrogen exchange factors measured by solution nuclear magnetic resonance spectroscopy as indicators of the structure and topology of membrane proteins.
Deuterium/hydrogen exchange factors (chi) were measured for the backbone amide sites of the membrane-bound forms of the 50-residue fd coat protein and the 23-residue magainin2 peptide in lipid micelles by solution nuclear magnetic resonance spectroscopy. By combining kinetic and thermodynamic effects, deuterium/hydrogen exchange factors overcome the principal limitations encountered in the measurements of kinetic protection factors and thermodynamic fractionation factors for membrane proteins. The magnitudes of the exchange factors can be correlated with the structure and topology of membrane-associated polypeptides. In fd coat protein, residues in the transmembrane helix have exchange factors that are substantially smaller than those in the amphipathic surface helix or the loop connecting the two helices. For the amphipathic helical peptide, magainin2, the exchange factors of residues exposed to the solvent are appreciably larger than those that face the hydrocarbon portion of membrane bilayers. These examples demonstrate that deuterium/hydrogen exchange factors can be measured by solution NMR spectroscopy and used to identify residues in transmembrane helices as well as to determine the polarity of amphipathic helices in membrane proteins.
Veglia
Gianluigi
G
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Zeri
Ana Carolina
AC
Ma
Che
C
Opella
Stanley J
SJ
D023181:Antimicrobial Cationic Peptides / Q000737:chemistry; D055592:Biophysical Phenomena; D001703:Biophysics; D002462:Cell Membrane / Q000378:metabolism*; D003903:Deuterium / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry; D054806:Magainins; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008823:Micelles; D008954:Models, Biological; D013053:Spectrophotometry; D013816:Thermodynamics; D013997:Time Factors; D029867:Xenopus Proteins
D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D054806:Magainins; D008823:Micelles; D029867:Xenopus Proteins; C053301:magainin 2 peptide, Xenopus; D006859:Hydrogen; D003903:Deuterium