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An ATP transporter is required for protein translocation into the yeast endoplasmic reticulum.
Author(s) -
Mayinger P.,
Meyer D.I.
Publication year - 1993
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1993.tb05699.x
Subject(s) - endoplasmic reticulum , chromosomal translocation , vesicle , translocon , yeast , transport protein , atp binding cassette transporter , biology , vesicular transport protein , biochemistry , transporter , microbiology and biotechnology , gene , membrane
The transfer of precursor proteins through the membrane of the rough endoplasmic reticulum (ER) in yeast is strictly dependent on the presence of ATP. Since Kar2p (the yeast homologue of mammalian BiP) is required for translocation, and is an ATP binding protein, an ATP transport system must be coupled to the translocation machinery of the ER. We report here the characterization of a transport system for ATP in vesicles derived from yeast ER. ATP uptake into vesicles was found to be saturable in the micromolar range with a Km of 1 × 10(−5) M. ATP transport into ER vesicles was specifically inhibited by 4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid (DIDS), a stilbene derivative known to inhibit a number of other anion transporters, and by 3′‐O‐(4‐benzoyl)benzoyl‐ATP (Bz2‐ATP). Inhibition of ATP uptake into yeast microsomes by DIDS and Bz2‐ATP blocked protein translocation in vitro measured co‐ as well as post‐translationally. The inhibitory effect of DIDS on translocation was prevented by coincubation with ATP. Moreover, selective membrane permeabilization, allowing ATP access to the lumen, restored translocation activity to DIDS‐treated membranes. These results demonstrate that translocation requires a DIDS and Bz2‐ATP‐sensitive component whose function is to transport ATP to the lumen of the ER. These findings are consistent with current models of protein translocation in yeast which stipulate the participation of Kar2p in the translocation process.