Nuclear envelope membranes

Rolls, M.M., Stein, P.A., Taylor, S.S., Ha, E., McKeon, F. and Rapoport, T.A. (1999) A visual screen of a GFP-fiision library identifies a new type of nuclear envelope membrane protein. J. Cell Biol. 146, 29A4. 

Of the less widely used analogues of ATP, 6-[(2,4-dinitrophenyl)thio]-9-p-D-ribofuranosylpurine 5 -triphosphate has been used for labelling an ATPase activity in rat liver nuclear envelope membranes, and 6-[(3-carboxy-4-nitro-phenyl)thio]-9-(3-D-ribofuranosylpurine 5 -triphosphate has been used to differentiate different classes of binding site in [Na+ + K+]-ATPase. ... 

Pfaller, R., and Newport, J. W. (1995). Assembly/disassembly of the nuclear envelope membrane. J. Biol Chem. 270, 19066-19072. 

Nuclear envelope membrane. is more complex than a double... 

Endothelial cells of brain arteries, veins and capillaries of the Wistar rat showed a positive NADPH-diaphorase (EC 1.6.99.1) reaction in form of 2-(2 -benzothiazolyl) - 5 - styryl - 3 - (4 - phthal - hydrazidyl) tetrazolium chloride-formazan contrast at the nuclear envelope, membranes of mitochondria and endoplasmic reticulum (Stanarius et al. 1997). Endothelial nitric oxide synthase (EC 1.14.23) immu-nostaining without tyramide signal amplification yielded electron dense 3,3 -diaminobenzidine precipitates that were seen in the endothelium if arteries, veins and some capillaries. Its pattern corresponded roughly with the membrane-bound 2-(2 -benzothiazolyl) - 5 - styryl - 3 - (4 - phthal-hydrazidyl) tetrazolium chloride-formazan deposits generated by NADPH-diaphorase. 

Nucleus The nucleus is separated from the cytosol by a double membrane, the nuclear envelope. The DNA is complexed with basic proteins (histones) to form chromatin fibers, the material from which chromosomes are made. A distinct RNA-rich region, the nucleolus, is the site of ribosome assembly. The nucleus is the repository of genetic information encoded in DNA and organized into chromosomes. During mitosis, the chromosomes are replicated and transmitted to the daughter cells. The genetic information of DNA is transcribed into RNA in the nucleus and passes into the cytosol where it is translated into protein by ribosomes. 

A system of membrane enclosed cisternae in the cytoplasm. The ER is continuous with the outer membrane of the nuclear envelope. The part of the ER coated with ribosomes is called rough ER, the other part is called smooth-surfaced ER. The rough ER is the first compartment of the secretory pathway. Here, membrane proteins are integrated into and secretory proteins translocated across the ER membrane. Furthermore,... 

In terms of evolutionary biology, the complex mitotic process of higher animals and plants has evolved through a progression of steps from simple prokaryotic fission sequences. In prokaryotic cells, the two copies of replicated chromosomes become attached to specialized regions of the cell membrane and are separated by the slow intrusion of the membrane between them. In many primitive eukaryotes, the nuclear membrane participates in a similar process and remains intact the spindle microtubules are extranuclear but may indent the nuclear membrane to form parallel channels. In yeasts and diatoms, the nuclear membrane also remains intact, an intranuclear polar spindle forms and attaches at each pole to the nuclear envelope, and a single kinetochore microtubule moves each chromosome to a pole. In the cells of higher animals and plants, the mitotic spindle starts to form outside of the nucleus, the nuclear envelope breaks down, and the spindle microtubules are captured by chromosomes (Kubai, 1975 Heath, 1980 Alberts et al., 1989). 

Ca2+ is the main intracellular signalling molecule in smooth muscle. Fluctuation in local cytoplasmic [Ca2+] near Ca2+-sensitive effector molecules allows for specific regulation of multiple functions. These temporal fluctuations and spatial variations of cytoplasmic [Ca2+] are dependent on the interactions of ion transport proteins located in the plasma membrane (PM) and membranes of the sacoplasmic reticulum (SR), nuclear envelope and mitochondria. These... 

In addition to forming close contacts with the PM, the SR network also comes into close contact with the mitochondria (Nixon et al 1994, Rizzuto et al 1998), forming yet another diffusionally restricted space (Fig. 4, panel E-G). This space, approximately 60—80 nm wide and sandwiched between the SR and mitochondrial membranes, also appears to be functionally important. As the SR network penetrates deeper into the cell, it inserts into the nuclear membrane such that the lumen of the perinuclear SR network is continuous with the lumen of the nuclear envelope (Somlyo 1985). 

The er is a three-dimensional membrane system (57-62). As visualized in a transmission electron microscope, there are two parallel membranes with an intervening electron transparent space, the lumen. The form and abundance of the er vary. The rer are flattened sacs with numerous attached ribosomes (15-20 nm). In contrast, the smooth er (ser) lacks ribosomes. The er seems to function as a communication system within cells and can be continuous with the outer nuclear envelope. Although the rer is involved in protein synthesis, the ser functions in glycosylation. 

The process of infection of lupine nodule cells by Rhizobia was examined by the thin-section electron microscopic technique, as well as the freeze-fracture technique. Different membranes such as infection thread membranes, peribacterioid membranes, plasma membranes, membranes of cytoplasmic vesicles, and membranes of the Golgi bodies and ER were stained with uranium-lead, silver, phosphotungstic acid, and ZIO (31). ZIO stained the membranes of the proximal face of the Golgi bodies and endoplasmic reticulum. ZIO staining has given good contrast in thick sections such as a cotyledon cell, a root cell, and an aleurone layer for ER, dictyosomes cisternae, mitochondria, and nuclear envelopes (17,32-37). 

The nuclear envelope is composed of the nuclear membranes (inner and outer), the nuclear lamina, and the nuclear pore complexes. The inner and outer nuclear membranes are connected at the nuclear pore sites and enclose a flattened sac... 

The nucleus is surrounded by the nuclear envelope, which takes on a lumenal structure connected to the endoplasmic reticulum. The transport of proteins into (and out of) the nucleus occurs through the nuclear pore complex (NPC), a large complex composed of more than 100 different proteins (Talcott and Moore, 1999). Because NPC forms an aqueous pore across the two membranes, small proteins less than 9 nm in diameter can pass through it simply by diffusion. However, most of the transports of both proteins and RNAs are mediated by an active transport mechanism. It is now clear that there is heavy traffic through the NPC in both directions. Proteins are not only imported into the nucleus but also actively exported from it as well. There are many reasons for nuclear export. One reason is to send some shuttle proteins back after their import another is for some viral proteins to export their replicated genomes outside the nucleus. 

Nucleus The nucleus serves as the cell s command center, sending directions to the cell to grow, mature, divide, or die. It also houses DNA (deoxyribonucleic acid), the cell s hereditary material. The nucleus is surrounded by a membrane called the nuclear envelope, which protects the DNA and separates the nucleus from the rest of the cell. 

Nuclear Envelope The membrane system of the cell nucleus that surrounds the nucleoplasm. It consists of two concentric membranes separated by the perinuclear space. The structures of the envelope where it opens to the cytoplasm are called the nuclear pores (nudear pore). [NIH]... 

Figure 20.28 Diagrammatic representation of mitosis in a cell with a single pair of homologous chromosomes. In prophase, the chromatin condenses into chromosomes, each of which consists of a pair of chromatids that have been formed by replication during interphase, and the nuclear envelope disappears. In metaphase, each chromatid attaches to the spindle fibres (microtubules) at a centre point, the centromere. In anaphase, the two chromatids of each chromosome become detached from each other and move to opposite poles of the cell along the microtubules. In telophase, the chromatids have reached the poles. Two nuclear envelopes then form and enclose each new set of chromatids, now once again called chromosomes. The microtubules disappear and the chromosomes uncoil and re-form into the long chromatin threads. Finally the cell membrane is drawn inward by a band of microfilaments to form a complete constriction between the newly formed nuclei, and two new cells are formed. The process is called cytokinesis.

The nucleus is separated from the cytoplasm by the nuclear envelope, which consists of the outer and inner nuclear membranes. Each of the two nuclear membranes has two layers, and the membranes are separated from each other by the perinuclear space. The outer nuclear membrane is continuous with the rough endoplasmic reticulum and is covered with ribosomes. The inner side of the membrane is covered with a protein layer (the nuclear lamina), in which the nuclear structures are anchored. 

There are two general kinds of cells those having a membrane-bounded nucleus called eukaryotic cells, and those without a nuclear envelope called prokaryotic cells. Humans have eukaryotic cells. All eukaryotic cells contain a nucleus that contains the genome, the complete set of genes. Unless noted otherwise, our discussion will be restricted to eukaryotic cells. 

Ubc6/Doa2 28 localized at the ER-membrane/nuclear envelope, involved in ERAD, degradation of MATa2... 

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