Protein translocation across membranes.
Cellular membranes act as semipermeable barriers to ions and macromolecules. Specialized mechanisms of transport of proteins across membranes have been developed during evolution. There are common mechanistic themes among protein translocation systems in bacteria and in eukaryotic cells. Here we review current understanding of mechanisms of protein transport across the bacterial plasma membrane as well as across several organelle membranes of yeast and mammalian cells. We consider a variety of organelles including the endoplasmic reticulum, outer and inner membranes of mitochondria, outer, inner, and thylakoid membranes of chloroplasts, peroxisomes, and lysosomes. Several common principles are evident: (a) multiple pathways of protein translocation across membranes exist, (b) molecular chaperones are required in the cytosol, inside the organelle, and often within the organelle membrane, (c) ATP and/or GTP hydrolysis is required, (d) a proton-motive force across the membrane is often required, and (e) protein translocation occurs through gated, aqueous channels. There are exceptions to each of these common principles indicating that our knowledge of how proteins translocate across membranes is not yet complete.
Agarraberes
F A
FA
Department of Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
Dice
J F
JF
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001419:Bacteria; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D002736:Chloroplasts; D003593:Cytoplasm / Q000378:metabolism; D005057:Eukaryotic Cells; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008956:Models, Chemical; D018832:Molecular Chaperones / Q000378:metabolism; D015388:Organelles / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*
D018832:Molecular Chaperones; D011506:Proteins; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate