Re‐entering the translocon from the lumenal side of the endoplasmic reticulum. Studies on mutated carboxypeptidase yscY species

FEBS Letters

Deak, Peter M.¹  Wolf, Dieter H.¹  Plemper, Richard K.¹  Otto, Ralf T.² 

[1] Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany;Institut für Bioverfahrenstechnik, Universität Stuttgart, Allmandring 31, 70569 Stuttgart, Germany

关键词: Endoplasmic reticulum degradation;    Carboxypeptidase yscY;    Retrograde transport;    Endoplasmic reticulum;    Yeast Saccharomyces cerevisiae;   

DOI  :  10.1016/S0014-5793(98)01724-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Misfolded or unassembled secretory proteins are retained in the endoplasmic reticulum (ER) and subsequently degraded by the cytosolic ubiquitin-proteasome system. This requires their retrograde transport from the ER lumen into the cytosol, which is mediated by the Sec61 translocon. It had remained a mystery whether ER-localised soluble proteins are at all capable of re-entering the Sec61 channel de novo or whether a permanent contact of the imported protein with the translocon is a prerequisite for retrograde transport. In this study we analysed two new variants of the mutated yeast carboxypeptidase yscY, CPY*: a carboxy-terminal fusion protein of CPY* and pig liver esterase and a CPY* species carrying an additional glycosylation site at its carboxy-terminus. With these constructs it can be demonstrated that the newly synthesised CPY* chain is not retained in the translocation channel but reaches its ER lumenal side completely. Our data indicate that the Sec61 channel provides the essential pore for protein transport through the ER membrane in either direction; persistent contact with the translocon after import seems not to be required for retrograde transport.

【 授权许可】

Unknown