J. Biol. Chem. 275, 14550-14557 (2000)[PubMed:10799540]
In yeast, efficient protein transport across the endoplasmic reticulum (ER) membrane may occur co-translationally or post-translationally. The latter process is mediated by a membrane protein complex that consists of the Sec61p complex and the Sec62p-Sec63p subcomplex. In contrast, in mammalian cells protein translocation is almost exclusively co-translational. This transport depends on the Sec61 complex, which is homologous to the yeast Sec61p complex and has been identified in mammals as a ribosome-bound pore-forming membrane protein complex. We report here the existence of ribosome-free mammalian Sec61 complexes that associate with two ubiquitous proteins of the ER membrane. According to primary sequence analysis both proteins display homology to the yeast proteins Sec62p and Sec63p and are therefore named Sec62 and Sec63, respectively. The probable function of the mammalian Sec61-Sec62-Sec63 complex is discussed with respect to its abundance in ER membranes, which, in contrast to yeast ER membranes, apparently lack efficient post-translational translocation activity.
The process of assisting in the covalent and noncovalent assembly of single chain polypeptides or multisubunit complexes into the correct tertiary structure.
J. Biol. Chem. 275, 14550-14557 (2000)[PubMed:10799540]
In yeast, efficient protein transport across the endoplasmic reticulum (ER) membrane may occur co-translationally or post-translationally. The latter process is mediated by a membrane protein complex that consists of the Sec61p complex and the Sec62p-Sec63p subcomplex. In contrast, in mammalian cells protein translocation is almost exclusively co-translational. This transport depends on the Sec61 complex, which is homologous to the yeast Sec61p complex and has been identified in mammals as a ribosome-bound pore-forming membrane protein complex. We report here the existence of ribosome-free mammalian Sec61 complexes that associate with two ubiquitous proteins of the ER membrane. According to primary sequence analysis both proteins display homology to the yeast proteins Sec62p and Sec63p and are therefore named Sec62 and Sec63, respectively. The probable function of the mammalian Sec61-Sec62-Sec63 complex is discussed with respect to its abundance in ER membranes, which, in contrast to yeast ER membranes, apparently lack efficient post-translational translocation activity.
Protein involved in the intracellular transport of proteins from one location to another. All proteins (except the ones synthesized in mitochondria and plastids) are synthesized on ribosomes in the cytosol. Most proteins remain in the cytosol. Proteins with a signal sequence either become plasma membrane components or are exported from the cell of origin.
Protein involved in the transport of a molecule (metabolite, protein, etc), a ion or an electron across cell membranes, inside the cell or in a tissue fluid.
Protein which is transiently involved in the noncovalent folding, assembly and/or disassembly of other polypeptides or RNA molecules, including any transport and oligomerisation processes they may undergo, and the refolding and reassembly of protein and RNA molecules denatured by stress. Though involved in these processes, chaperones are not an integral part of these functioning molecules. Also used for metallochaperones, which function to provide a metal directly to target proteins while protecting this metal from scavengers.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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