A microsomal protein is involved in ATP-dependent transport of presecretory proteins into mammalian microsomes

P. Klappa, P. Mayinger, R. Pipkorn, M. Zimmermann, R. Zimmermann

Research output: Contribution to journalArticle

56 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)2795-2803
Number of pages9
JournalEMBO Journal
Issue number10
StatePublished - Oct 21 1991



  • Azido-ATP photoaffinity inactivation
  • Mammalian endoplasmic reticulum Protein transport

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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