title: The aromatic residues Trp and Phe have different effects on the positioning of a transmembrane helix in the microsomal membrane.
abstract: We have examined the effect of Trp and Phe residues on the positioning of a poly-Leu transmembrane helix relative to the microsomal membrane by employing a previously described "glycosylation mapping" technique [Nilsson, I. M., Sääf, A., Whitley, P., Gafvelin, G., Waller, C., and von Heijne, G. (1998) J. Mol. Biol. 284, 1165-1175]. Both Trp and Phe tend to push the transmembrane helix into the membrane when inserted in positions flanking the poly-Leu stretch, and Trp (but not Phe) pulls the transmembrane helix toward the lipid-water interface when inserted inside the poly-Leu segment. Thus, the preference of Trp for the lipid-water interface previously suggested on the basis of biophysical studies of model peptides can also be observed for a bona fide transmembrane helix in a biological membrane. We further show that a sufficiently long poly-Trp segment functions as an efficient stop-transfer sequence during protein translocation across the microsomal membrane, despite the preference of Trp residues for the lipid-water interface region.
authors.affiliation: Department of Biochemistry, Stockholm University, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Braun
authors.forename: G
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D007425:Intracellular Membranes / Q000737:chemistry* / Q000201:enzymology; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008861:Microsomes / Q000737:chemistry* / Q000201:enzymology; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D010455:Peptides; C027819:polyleucine; D010649:Phenylalanine; D014364:Tryptophan; D012697:Serine Endopeptidases; C026515:type I signal peptidase