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The general structure of the endoplasmic reticulum is a network of membranes called cisternae. These sac-like structures are held together by the cytoskeleton . The phospholipid membrane encloses the cisternal space (or lumen), which is continuous with the perinuclear space but separate from the cytosol .
Valosin-containing protein (VCP) or transitional endoplasmic reticulum ATPase (TER ATPase) also known as p97 in mammals and CDC48 in S. cerevisiae, is an enzyme that in humans is encoded by the VCP gene. [5] [6] [7] The TER ATPase is an ATPase enzyme present in all eukaryotes and archaebacteria.
The outer nuclear membrane is continuous with the rough endoplasmic reticulum membrane, and like that structure, features ribosomes attached to the surface. The outer membrane is also continuous with the inner nuclear membrane since the two layers are fused together at numerous tiny holes called nuclear pores that perforate the nuclear envelope.
In mammalian organisms, COPII vesicles that have budded from exit sites in the endoplasmic reticulum lose their coats and fuse to form the vesicular-tubular cluster (VTC). Retrieval (or retrograde) transport in COPI vesicles returns many of the lost ER resident proteins back to the endoplasmic reticulum. Forward (or anterograde) transport moves ...
The translocon (also known as a translocator or translocation channel) is a complex of proteins associated with the translocation of polypeptides across membranes. [1] In eukaryotes the term translocon most commonly refers to the complex that transports nascent polypeptides with a targeting signal sequence into the interior (cisternal or lumenal) space of the endoplasmic reticulum (ER) from ...
While the two membranes and the endoplasmic reticulum are linked, proteins embedded in the membranes tend to stay put rather than dispersing across the continuum. [18] It is lined with a fiber network called the nuclear lamina which is 10-40 nm thick and provides strength.
For example, in epithelial cells, a special process called transcytosis allows some materials to enter one side of a cell and exit from the opposite side. Also, in some circumstances, late endosomes/MVBs fuse with the plasma membrane instead of with lysosomes, releasing the lumenal vesicles, now called exosomes , into the extracellular medium.
The spine apparatus (SA) is a specialized form of endoplasmic reticulum (ER) that is found in a subpopulation of dendritic spines in central neurons.It was discovered by Edward George Gray in 1959 when he applied electron microscopy to fixed cortical tissue. [1]