The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER). The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae, and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa.
The signal recognition particle (SRP) is an abundant, cytosolic, universally conserved ribonucleoprotein that recognizes and targets specific proteins to the endoplasmic reticulum in eukaryotes and the plasma membrane in prokaryotes.
A signal peptide is a short peptide present at the N-terminus of most newly synthesized proteins that are destined toward the secretory pathway. These proteins include those that reside either inside certain organelles, secreted from the cell, or inserted into most cellular membranes. Although most type I membrane-bound proteins have signal peptides, the majority of type II and multi-spanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which biochemically resembles a signal sequence except that it is not cleaved. They are a kind of target peptide.
The translocon is a complex of proteins associated with the translocation of polypeptides across membranes. In eukaryotes the term translocon most commonly refers to the complex that transports nascent polypeptides with a targeting signal sequence into the interior space of the endoplasmic reticulum (ER) from the cytosol. This translocation process requires the protein to cross a hydrophobic lipid bilayer. The same complex is also used to integrate nascent proteins into the membrane itself. In prokaryotes, a similar protein complex transports polypeptides across the (inner) plasma membrane or integrates membrane proteins. In either case, the protein complex are formed from Sec proteins, with the heterotrimeric Sec61 being the channel. In prokaryotes, the homologous channel complex is known as SecYEG.
Calnexin (CNX) is a 67kDa integral protein (that appears variously as a 90kDa, 80kDa, or 75kDa band on western blotting depending on the source of the antibody) of the endoplasmic reticulum (ER). It consists of a large (50 kDa) N-terminal calcium-binding lumenal domain, a single transmembrane helix and a short (90 residues), acidic cytoplasmic tail.
The unfolded protein response (UPR) is a cellular stress response related to the endoplasmic reticulum (ER) stress. It has been found to be conserved between mammalian species, as well as yeast and worm organisms.
Glycoprotein IX (platelet) (GP9) also known as CD42a (Cluster of Differentiation 42a), is a human gene.
Autocrine motility factor receptor, isoform 2 is a protein that in humans is encoded by the AMFR gene.
Mitochondrial import receptor subunit TOM20 homolog is a protein that in humans is encoded by the TOMM20 gene. TOM20 is one of the receptor systems of the TOM complex in the outer mitochondrial membrane (OMM).
Protein transport protein Sec61 subunit beta is a protein that in humans is encoded by the SEC61B gene.
Minor histocompatibility antigen H13 is a protein that in humans is encoded by the HM13 gene.
Ceroid-lipofuscinosis neuronal protein 6 is a protein that in humans is encoded by the CLN6 gene.
Ribosome-binding protein 1, also referred to as p180, is a protein that in humans is encoded by the RRBP1 gene.
Protein transport protein Sec61 subunit alpha isoform 1 is a protein that in humans is encoded by the SEC61A1 gene.
Translocon-associated protein subunit beta also known as TRAP-beta is a protein that in humans is encoded by the SSR2 gene.
BET1 homolog is a protein that in humans is encoded by the BET1 gene.
Translocon-associated protein subunit delta is a protein that in humans is encoded by the SSR4 gene.
Junctophilin 2, also known as JPH2, is a protein which in humans is encoded by the JPH2 gene. Alternative splicing has been observed at this locus and two variants encoding distinct isoforms are described.
Signal recognition particle receptor subunit beta is a protein that in humans is encoded by the SRPRB gene.
Junctophilin-1 is a protein that in humans is encoded by the JPH1 gene.
