title: Protein translocation across and integration into membranes.
abstract: This review concentrates mainly on the translocation of proteins across the endoplasmic reticulum membrane and cytoplasmic membrane in bacteria. It will start with a short historical review and will pinpoint the crucial questions in the field. Special emphasis will be given to the present knowledge on the molecular details of the first steps, i.e., on the function of the signal recognition particle and its receptor. The knowledge on the signal peptidase and the ribosome receptor(s) will also be summarized. The various models for the translocation of proteins across and the integration of proteins into membranes will be critically discussed. In particular, the function of signal, stop-transfer, and insertion sequences will be dealt with and molecular differences discussed. The cotranslational mode of membrane transfer will be compared with the post-translational transport found for mitochondria and chloroplasts. This review will conclude with open questions and an outlook.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000378:metabolism; D001693:Biological Transport, Active; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D007328:Insulin; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D011384:Proinsulin / Q000378:metabolism; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D012261:Ribonucleoproteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D012697:Serine Endopeptidases; D018271:Signal Recognition Particle
chemical_list: D007328:Insulin; D008565:Membrane Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011506:Proteins; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D012261:Ribonucleoproteins; D018271:Signal Recognition Particle; C036318:signal peptide receptor; C013737:preproinsulin; D011384:Proinsulin; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase