title: The tyrosine-containing internalization motif in the cytoplasmic domain of TGN38/41 lies within a nascent helix.
abstract: TGN38 and TGN41 are isoforms of an integral membrane protein (TGN38/41) which is predominantly located in the trans-Golgi network of mammalian cells, but which constitutively recycles between the TGN and the plasma membrane. The cytoplasmic domain tetrapeptide sequence "YQRL" is responsible for the internalization of TGN38/41 from the plasma membrane. This sequence conforms to the tyrosine containing internalization motif ("YXXhydro," where X is any amino acid and hydro is any large bulky hydrophobic amino acid) found in other integral membrane proteins which are internalized from the plasma membrane via clathrin-coated vesicles. Structural predictions have suggested that the YXXhydro motif might adopt a tight turn structure in solution, a prediction supported previously by nuclear magnetic resonance (NMR) studies on short synthetic peptides corresponding to variants of the generic YXXhydro motif. We have synthesized a 21-amino acid peptide which encompasses the TGN38/41 internalization motif and used it as template for two-dimensional NMR analysis. The data from these experiments demonstrate that the internalization motif in the cytoplasmic domain of TGN38/41 lies within a nascent helix, not a tight turn. This is the first study to show that tyrosine containing internalization motifs do not necessarily adopt a beta-turn conformation.
authors.affiliation: Department of Biochemistry, School of Medical Sciences, University of Bristol, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Wilde
authors.forename: C
authors.initials: C
authors.lastname: Dempsey
authors.forename: G
authors.initials: G
authors.lastname: Banting
mesh_terms: D000595:Amino Acid Sequence; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D006023:Glycoproteins; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D011487:Protein Conformation; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D014443:Tyrosine