title: Proline-induced disruption of a transmembrane alpha-helix in its natural environment.
abstract: alpha-Helix formation in globular proteins has been studied both theoretically and experimentally for decades, while a lack of both high-resolution structures and suitable experimental techniques has hampered the study of helices in membrane proteins. We have developed a new experimental approach, glycosylation mapping, where the active site of the lumenally exposed endoplasmic reticulum enzyme oligosaccharyl transferase is used as a point of reference against which the position of a transmembrane segment in the membrane can be measured. Here, we report an initial analysis of the helix-breaking properties of proline residues inserted in a transmembrane helix. We find that proline residues can break a transmembrane helix, but only when inserted near the end, and only when the helix is sufficiently long. The glycosylation mapping technique may be generally useful for determining the position of transmembrane helices in the membrane.
authors.affiliation: Department of Biochemistry, Stockholm University, Stockholm, S-106 91, Sweden.
authors.forename: I
authors.initials: I
authors.lastname: Nilsson
authors.forename: A
authors.initials: A
authors.lastname: Sääf
authors.forename: P
authors.initials: P
authors.lastname: Whitley
authors.forename: G
authors.initials: G
authors.lastname: Gafvelin
authors.forename: C
authors.initials: C
authors.lastname: Waller
authors.forename: G
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D004721:Endoplasmic Reticulum / Q000201:enzymology; D004926:Escherichia coli / Q000235:genetics; D006031:Glycosylation; D006602:Hexosyltransferases; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012242:Rhodobacter sphaeroides / Q000737:chemistry / Q000235:genetics; D014166:Transferases / Q000737:chemistry
chemical_list: D008051:Lipid Bilayers; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D011994:Recombinant Proteins; D011392:Proline; D014166:Transferases; D006602:Hexosyltransferases; C025620:dolichyl-diphosphooligosaccharide - protein glycotransferase