title: Sec dependent and sec independent assembly of E. coli inner membrane proteins: the topological rules depend on chain length.
abstract: Translocation of proteins across the inner membrane of Escherichia coli normally requires the participation of the sec machinery. A number of proteins are known, however, where translocation can proceed unhindered even when the function of either SecA or SecY, central components of the sec machinery, is blocked. We now show that there is a linear correlation between the length of a translocated region and its degree of dependence on SecA and SecY for lengths between 25 and 55 residues. We also find that positively charged residues have distinctly different topological effects during SecA dependent and SecA independent membrane protein insertion, and that a short cytoplasmic segment in Lep can be converted to a translocated segment (with a concomitant inversion of the original topology of the whole molecule) by increasing its length into the SecA/Y dependent realm.
authors.affiliation: Department of Molecular Biology, Karolinska Institute Center for Structural Biochemistry, NOVUM, Huddinge, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Andersson
authors.forename: G
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D004563:Electrochemistry; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D012697:Serine Endopeptidases
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C057841:SecY protein, E coli; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins