Abstract
Most secreted and membrane proteins are targeted to and translocated across the endoplasmic reticulum (ER) membrane through the Sec61 protein-conducting channel. Evolutionarily conserved Sec62 and Sec63 associate with the Sec61 channel, forming the Sec complex and mediating translocation of a subset of proteins. For the last three decades, it has been thought that ER protein targeting and translocation occur via two distinct pathways: signal recognition particle (SRP)-dependent co-translational or SRP-independent, Sec62/Sec63 dependent post-translational translocation pathway. However, recent studies have suggested that ER protein targeting and translocation through the Sec translocon are more intricate than previously thought. This review summarizes the current understanding of the molecular functions of Sec62/Sec63 in ER protein translocation.
Highlights
One-third of the eukaryotic proteome is directed to the endoplasmic reticulum (ER) for localization in the organelles of the secretory pathway or secreted out of the cells
When different test proteins of varying hydrophobicity and the C-terminal length were assessed for their translocation efficiency in microsomes isolated from or semipermeabilized human cells depleted of Sec62, post-translational translocation of preproapelin, a small secretory protein, was reduced, whereas both co- and post-translational translocation of preproapelin was impaired in the cells depleted of Sec63 [54,55]
Studies to date have shown that evolutionarily conserved Sec62 mediates the translocation of proteins with specific characteristics
Summary
One-third of the eukaryotic proteome is directed to the ER for localization in the organelles of the secretory pathway or secreted out of the cells. In their N-terminus, which targets them to the ER. These proteins are thought to be translocated across or inserted into the ER membrane via the Sec protein-conducting channel co-translationally or through the Sec complex post-translationally that contains. Recent ER-proximity ribosome profiling studies have shown that most ER protein targeting occurs in a co-translational manner [2,3]. In contrast to the ribosome profiling results, cryo-electron microscopy (EM) structures of the yeast Sec complex show that the. Sec complex is not compatible for co-translational translocation because the ribosome and. We summarize the classical and emerging views on protein targeting and translocation via the Sec complex, and discuss the underlying mechanisms and molecular functions of the.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
