title: TIM23-mediated insertion of transmembrane α-helices into the mitochondrial inner membrane.
abstract: While overall hydrophobicity is generally recognized as the main characteristic of transmembrane (TM) α-helices, the only membrane system for which there are detailed quantitative data on how different amino acids contribute to the overall efficiency of membrane insertion is the endoplasmic reticulum (ER) of eukaryotic cells. Here, we provide comparable data for TIM23-mediated membrane protein insertion into the inner mitochondrial membrane of yeast cells. We find that hydrophobicity and the location of polar and aromatic residues are strong determinants of membrane insertion. These results parallel what has been found previously for the ER. However, we see striking differences between the effects elicited by charged residues flanking the TM segments when comparing the mitochondrial inner membrane and the ER, pointing to an unanticipated difference between the two insertion systems.
authors.affiliation: Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, Stockholm, Sweden.
authors.forename: Salomé Calado
authors.initials: SC
authors.lastname: Botelho
authors.forename: Marie
authors.initials: M
authors.lastname: Osterberg
authors.forename: Andreas S
authors.initials: AS
authors.lastname: Reichert
authors.forename: Koji
authors.initials: K
authors.lastname: Yamano
authors.forename: Patrik
authors.initials: P
authors.lastname: Björkholm
authors.forename: Toshiya
authors.initials: T
authors.lastname: Endo
authors.forename: Gunnar
authors.initials: G
authors.lastname: von Heijne
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae