title: A microsomal protein is involved in ATP-dependent transport of presecretory proteins into mammalian microsomes.
abstract: Ribonucleoparticle (i.e. ribosome and SRP)-independent transport of proteins into mammalian microsomes is stimulated by a cytosolic ATPase which involves proteins belonging to the hsp70 family. Here we addressed the question of whether there are additional nucleoside triphosphate requirements involved in this transport mechanism. We employed a purified presecretory protein which upon solubilization in dimethyl sulfoxide and subsequent dilution into an aqueous buffer was processed by and transported into mammalian microsomes in the absence of the cytosolic ATPase. Membrane insertion of this precursor protein was found to depend on the hydrolysis of ATP and to involve a microsomal protein which can be photoaffinity inactivated with azido-ATP. Furthermore, a microsomal protein with a similar sensitivity towards photoaffinity modification with azido-ATP was observed to be involved in ribonucleoparticle-dependent transport. We suggest that a novel microsomal protein which depends on ATP hydrolysis is involved in membrane insertion of both ribonucleoparticle-dependent and -independent precursor proteins.
authors.affiliation: Institut für Physiologische Chemie und Physikalische Biochemie, Universität München, FRG.
authors.forename: P
authors.initials: P
authors.lastname: Klappa
authors.forename: P
authors.initials: P
authors.lastname: Mayinger
authors.forename: R
authors.initials: R
authors.lastname: Pipkorn
authors.forename: M
authors.initials: M
authors.lastname: Zimmermann
authors.forename: R
authors.initials: R
authors.lastname: Zimmermann
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*; D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000737:chemistry; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D006868:Hydrolysis; D007301:Insect Hormones / Q000378:metabolism*; D019476:Insect Proteins; D008861:Microsomes / Q000378:metabolism*; D018832:Molecular Chaperones; D010179:Pancreas / Q000378:metabolism; D010777:Photochemistry; D011498:Protein Precursors / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D001386:Azides; D002352:Carrier Proteins; C059037:CecA2 protein, Bombyx mori; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D007301:Insect Hormones; D019476:Insect Proteins; D018832:Molecular Chaperones; D011498:Protein Precursors; D011506:Proteins; C017040:8-azidoadenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases