Biomaterial Database

Mechanism of signal-anchor triage during early steps of membrane protein insertion. 2023

Haoxi Wu, and Ramanujan S Hegde

MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.

Most membrane proteins use their first transmembrane domain, known as a signal anchor (SA), for co-translational targeting to the endoplasmic reticulum (ER) via the signal recognition particle (SRP). The SA then inserts into the membrane using either the Sec61 translocation channel or the ER membrane protein complex (EMC) insertase. How EMC and Sec61 collaborate to ensure SA insertion in the correct topology is not understood. Using site-specific crosslinking, we detect a pre-insertion SA intermediate adjacent to EMC. This intermediate forms after SA release from SRP but before ribosome transfer to Sec61. The polypeptide's N-terminal tail samples a cytosolic vestibule bordered by EMC3, from where it can translocate across the membrane concomitant with SA insertion. The ribosome then docks on Sec61, which has an opportunity to insert those SAs skipped by EMC. These results suggest that EMC acts between SRP and Sec61 to triage SAs for insertion during membrane protein biogenesis.

UI	MeSH Term	Description	Entries
D008565	Membrane Proteins	Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.	Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D004721	Endoplasmic Reticulum	A system of cisternae in the CYTOPLASM of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (CELL MEMBRANE) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced (ENDOPLASMIC RETICULUM, ROUGH); otherwise it is said to be smooth-surfaced (ENDOPLASMIC RETICULUM, SMOOTH). (King & Stansfield, A Dictionary of Genetics, 4th ed)	Ergastoplasm,Reticulum, Endoplasmic
D000069816	SEC Translocation Channels	Universally conserved multiprotein complexes that form the protein transport channel of the general secretory (SEC) pathway. The SEC translocase is present in all bacteria, archaea, and eukaryotes. It is in the ENDOPLASMIC RETICULUM membrane of eukaryotic cells, in the THYLAKOID MEMBRANE in CHLOROPLASTS and in some protozoa in the INNER MITOCHONDRIAL MEMBRANE.	SEC Translocation Channel,SEC Translocon,SEC61 Translocation Channel,Sec Protein Translocation System,SecYEG Protein,SecYEG Translocation Channel,SEC Complexes,SEC Translocase,SEC Translocons,SEC61 Protein,SEC61 Proteins,SEC61 Translocase,SEC61 Translocation Channels,SEC61 Translocon,Sec Protein Translocation Systems,Sec61 Complex,Sec61 Protein Translocation System,SecY Translocase,SecYEG Complex,SecYEG Complexes,SecYEG Protein Translocation System,SecYEG Proteins,SecYEG Translocation Channels,SecYEG Translocon,Channel, SEC Translocation,Channel, SEC61 Translocation,Channel, SecYEG Translocation,Channels, SEC Translocation,Channels, SEC61 Translocation,Channels, SecYEG Translocation,Complex, Sec61,Complex, SecYEG,Complexes, SEC,Complexes, SecYEG,Protein, SEC61,Protein, SecYEG,Proteins, SEC61,Proteins, SecYEG,Translocase, SEC,Translocase, SEC61,Translocase, SecY,Translocation Channel, SEC,Translocation Channel, SEC61,Translocation Channel, SecYEG,Translocation Channels, SEC,Translocation Channels, SEC61,Translocation Channels, SecYEG,Translocon, SEC,Translocon, SEC61,Translocon, SecYEG,Translocons, SEC
D014218	Triage	The sorting out and classification of patients or casualties to determine priority of need and proper place of treatment.	Triages
D018271	Signal Recognition Particle	A cytosolic ribonucleoprotein complex that acts to induce elongation arrest of nascent presecretory and membrane proteins until the ribosome becomes associated with the rough endoplasmic reticulum. It consists of a 7S RNA and at least six polypeptide subunits (relative molecular masses 9, 14, 19, 54, 68, and 72K).	SRP (Signal Recognition Particle),Particle, Signal Recognition,Recognition Particle, Signal
D021381	Protein Transport	The process of moving proteins from one cellular compartment (including extracellular) to another by various sorting and transport mechanisms such as gated transport, protein translocation, and vesicular transport.	Cellular Protein Targeting,Gated Protein Transport,Protein Targeting, Cellular,Protein Translocation,Transmembrane Protein Transport,Vesicular Protein Transport,Protein Localization Processes, Cellular,Protein Sorting,Protein Trafficking,Protein Transport, Gated,Protein Transport, Transmembrane,Protein Transport, Vesicular,Traffickings, Protein