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ER import of small human presecretory proteins: components and mechanisms
Author(s) -
Haßdenteufel Sarah,
Nguyen Duy,
Helms Volkhard,
Lang Sven,
Zimmermann Richard
Publication year - 2019
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1002/1873-3468.13542
Subject(s) - sec61 , endoplasmic reticulum , translocon , ribosome , translation (biology) , microbiology and biotechnology , membrane protein , chemistry , biology , biochemistry , membrane , gene , rna , messenger rna
Protein transport into the mammalian endoplasmic reticulum (ER) used to be seen as strictly cotranslational, that is temporarily and mechanistically coupled to protein synthesis. In the course of the last decades, however, several classes of precursors of soluble and membrane proteins were found to be post‐translationally imported into the ER, without any involvement of the ribosome. The first such class to be identified were the small presecretory proteins; tail‐anchored membrane proteins followed next. In both classes, the inherent address tag is released from the translating ribosome before the initiation of ER import, as part of the fully synthesized precursor. In small presecretory proteins, the information for ER targeting and ‐translocation via the polypeptide‐conducting Sec61‐channel is encoded by a classical N‐terminal signal peptide, which is released from the ribsosome before targeting due to the small size of the full‐length precursor. Here, we discuss the current state of research on targeting and translocation of small presecretory proteins into the mammalian ER. In closing, we present a unifying hypothesis for ER protein translocation in terms of an energy diagram for Sec61‐channel gating.