title: Membrane-bound peptides mimicking transmembrane Vph1p helix 7 of yeast V-ATPase: a spectroscopic and polarity mismatch study.
abstract: The V-ATPases are a family of ATP-dependent proton pumps, involved in a variety of cellular processes, including bone breakdown. V-ATPase enzymes that are too active in the latter process can result in osteoporosis, and inhibitors of the enzyme could be used to treat this disease. As a first step in studying the structure and function of the membrane-embedded interface at which proton translocation takes place, and its role in V-ATPase inhibition, synthetic peptides P1 and P2 consisting of 25 amino acid residues are presented here that mimic Vph1p helix 7 of yeast V-ATPase. A single mutation R10A between peptide P1 and P2 makes it possible to focus on the role of the essential arginine residue R735 in proton translocation. In the present work, we use a novel combination of spectroscopic techniques, such as CD spectroscopy, tryptophan emission spectra, acrylamide quenching and parallax analysis, and polarity mismatch modeling to characterize the peptides P1 and P2 in lipid bilayer systems. Based on both the spectroscopic experiments and the polarity mismatch modeling, P1 and P2 adopt a similar transmembrane conformation, with a mainly alpha-helical structure in the central part, placing the tryptophan residue at position 12 at a location 4+/-2 A from the centre of the lipid bilayer. Furthermore, the arginine at position 10 in P1 does not have an effect on the bilayer topology of the peptide, showing that the long, flexible side chain of this residue is able to snorkel towards the lipid headgroup region. This large flexibility of R735 might be important for its function in proton translocation in the V-ATPase enzyme.
authors.affiliation: Laboratory of Biophysics, Wageningen University, Dreijenlaan 3, NL-6703 HA, P.O. Box 8128, 6700 ET Wageningen, The Netherlands.
authors.forename: Renske W
authors.initials: RW
authors.lastname: Hesselink
authors.forename: Rob B M
authors.initials: RB
authors.lastname: Koehorst
authors.forename: Petr V
authors.initials: PV
authors.lastname: Nazarov
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Hemminga
mesh_terms: D020106:Acrylamide / Q000737:chemistry / Q000494:pharmacology; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D001120:Arginine / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism*; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D006639:Histidine / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry; D008055:Lipids / Q000737:chemistry; D015233:Models, Statistical; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014364:Tryptophan / Q000737:chemistry; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D008051:Lipid Bilayers; D008055:Lipids; D010455:Peptides; D020106:Acrylamide; D006639:Histidine; D014364:Tryptophan; D001120:Arginine; D025262:Vacuolar Proton-Translocating ATPases