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

• Published in: The EMBO journal 1991-10, Vol.10 (10), p.2795-2803
• Main Authors: Klappa, P., Mayinger, P., Pipkorn, R., Zimmermann, M., Zimmermann, R.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - analogs & derivatives; Adenosine Triphosphate - chemistry; Adenosine Triphosphate - metabolism; Affinity Labels; Animals; ATP; Azides - chemistry; Biological and medical sciences; Biological Transport, Active; Carrier Proteins - metabolism; Cell Membrane - metabolism; Cell physiology; dependent; Dogs; endoplasmic reticulum; Endoplasmic Reticulum Chaperone BiP; Fundamental and applied biological sciences. Psychology; Heat-Shock Proteins; Hydrolysis; identification; Insect Hormones - metabolism; Insect Proteins; Membrane and intracellular transports; membrane proteins; Microsomes - metabolism; Molecular and cellular biology; Molecular Chaperones; Pancreas - metabolism; Photochemistry; Protein Precursors - metabolism; proteins; Proteins - metabolism; requirements; transport
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1991.tb07828.x

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.