title: Hydrogen exchange in the lipid bilayer-bound gramicidin channel.
abstract: Hydrogen exchange experiments for a membrane-bound polypeptide could lead to interesting functional and structural insights. Here, hydrogen/deuterium exchange, saturation transfer and differential relaxation experiments have been performed on oriented lipid bilayer-bound polypeptide samples to measure the exchange lifetimes. The polypeptide, gramicidin A, forms a monovalent cation selective channel across membranes. The pH dependent results suggest that the indole N epsilon 1-H groups show base catalyzed hydrogen exchange, but that the backbone amide sites are not base catalyzed, consistent with the exclusion of anions from this channel. Furthermore, the recently described [1] orientational distribution of the individual peptide carbonyls (i.e. carbonyls either tipped slightly in toward or away from the channel axis) is consistent with the observed difference in odd- and even-numbered amide residue exchange lifetimes.
authors.affiliation: Department of Chemistry, Florida State University, Tallahassee 32306-4005, USA.
authors.forename: S
authors.initials: S
authors.lastname: Huo
authors.forename: S
authors.initials: S
authors.lastname: Arumugam
authors.forename: T A
authors.initials: TA
authors.lastname: Cross
mesh_terms: D003903:Deuterium; D006096:Gramicidin / Q000737:chemistry* / Q000378:metabolism; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D006096:Gramicidin; D006859:Hydrogen; D003903:Deuterium