Reference: Jung SJ, et al. (2019) Proper insertion and topogenesis of membrane proteins in the ER depend on Sec63. Biochim Biophys Acta Gen Subj 1863(9):1371-1380

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Abstract


Background: In eukaryotic cells, biogenesis of proteins destined to the secretory pathway begins from the cytosol. Nascent chains are either co-translationally or post-translationally targeted to the endoplasmic reticulum (ER) and translocated across the membrane through the Sec61 complex. For the post-translational translocation, the Sec62/Sec63 complex is additionally required. Sec63, however, is also shown to mediate co-translational translocation of a subset of proteins, the types and characteristics of proteins that Sec63 mediates in translocation still await to be defined.

Methods: To overview the types of proteins that require Sec63 for the ER translocation, we prepared Sec63 mutant lacking the first 39 residues (Sec63_ΔN39) in yeast and assessed initial translocation efficiencies of diverse types of precursors in the sec63_ΔN39 strain by a 5 min metabolic labeling. By employing Blue-Native gel electrophoresis (BN-PAGE), stability of the SEC complex (Sec61 plus Sec62/Sec63 complexes) isolated from cells carrying the Sec63_ΔN39 mutant was examined.

Results: Among the various translocation precursors tested, we found that proper sorting of single- and double-pass membrane proteins was severely impaired in addition to post-translational translocation precursor in the sec63_ΔN39 mutant strain. Stability of the SEC complex was compromised upon deletion of the N-terminal 39 residues.

Conclusions: The N-terminus of Sec63 is important for stability of the SEC complex and Sec63 is required for proper sorting of membrane proteins in vivo.

General significance: Sec63 is essential on insertion of membrane proteins.

Reference Type
Journal Article | Research Support, Non-U.S. Gov't
Authors
Jung SJ, Jung Y, Kim H
Primary Lit For
SEC63
Additional Lit For
DAP2 | SEC62-SEC63 complex

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