Lamin proteins

Nuclear lamin proteins and the Ras proteins were later shown to be modified by this prenylation reaction [4-6]. The prenyl molecule involved was foimd to be a 15-carbon farnesyl moiety attached to a C-terminal cysteine by a thioether bond [5,6]. Since these farnesylated targets were involved in cell division and signal transduction associated with cell proliferation, the findings suggested an important role for this pathway in tumor cell... 

Intermediate filaments are assemblies of intermediate filament proteins that provide mechanical strength to animal cells. Intermediate filaments include keratins, desmin filaments, vimentin filaments, nuclear lamins, and neurofilaments. The diameter of these filaments (about 10 nm) is intermediate between the thin actin filaments (about 7 nm) and the thicker microtubules (about 25 nm). Networks of cytoplasmic intermediate filaments are found throughout the cytoplasm of most animal cells, with some concentration around the nucleus. The lamin proteins make a network of intermediate filaments, the nuclear lamina, that lies just inside the nuclear membrane. 

Intermediate filaments are relatively stable. They are regulated, however, and this is seen most dramatically in mitosis when phosphorylation of the lamin proteins causes the disassembly of the nuclear lamina at the beginning of mitosis and dephosphorylation of the lamin proteins causes reassembly in two daughter nuclear laminae at the... 

Lehner, CF., Stick, R, Eppenbeiger, H.M. Nigg, E.A. (1987). Differential expression of nuclear lamin proteins during chicken development. ]. Cell Biol, 105, 577-87. 

The filamentous lamin proteins, in a manner similar to collagen, a-tropomyosin, and intermediate... 

Ghanbarzadeh, B. and Oromiehi, A. R. (2009).Thermal and mechanical behavior of laminated protein films. Journal of Food Engineering, 90(4), 517-524. 

In fine wool such as that obtained from merino sheep, the cuticle is normally one cell thick (20 x 30 x 0.5 mm, approximate dimensions) and usually constitutes about 10% by weight of the total fiber. Sections of cuticle cells show an internal series of laminations (Figs. 1 and 2) comprising outer sulfur-rich bands known as the exocuticle and inner regions of lower sulfur content called the endocuticle (13). On the exposed surface of cuticle cells, a membrane-like proteinaceous band (epicuticle) and a unique hpid component form a hydrophobic resistant barrier (14). These hpid and protein components are the functional moieties of the fiber surface and are important in fiber protection and textile processing (15). 

Rossieretal. [332] usedUV excimer laser photoablation to cut channels 50 microns deep by 100 microns wide in laminated PET. These channels were filled with PA, and rapid separation of proteins by isoelectric focusing was demonstrated. 

Two major types of muscle fibers are found in humans white (anaerobic) and red (aerobic). The former are particularly used in sprints and the latter in prolonged aerobic exercise. During a sprint, muscle uses creatine phosphate and glycolysis as energy sources in the marathon, oxidation of fatty acids is of major importance during the later phases. Nonmuscle cells perform various types of mechanical work carried out by the structures constituting the cytoskeleton. These strucmres include actin filaments (microfilaments), micrombules (composed primarily of a- mbulin and p-mbulin), and intermediate filaments. The latter include keratins, vimentin-like proteins, neurofilaments, and lamins. 

Associated with NA depletion from host nuclei was the diminution and deformation of these nuclei, significant depletion of host nucleoskeletal protein lamin b, and significant reductions in levels of host cell RNA, protein and acid phosphatase activity. In contrast, host infiltrating cells showed no such changes, supporting an infected cell-specific effect. These observations support the possibility that NA are synthesized by the parasite and modulate host nuclear functions. However, release of other parasite secretory products, not analysed, might have been inhibited in these experiments also. 

NA isolation and molecular characterization will be important to define the origin and functions of these proteins. At this time, infected cell nuclei offer the only source of these proteins, and NA have proved resistant to classic nuclear extraction methods (Yao and Jasmer, 1998). NA can be solubilized under conditions that co-extract nuclear lamins a/c and b (4 M urea, pH 8.0). Despite these similar physical properties, NA do not co-localize with lamins in the nucleoskeleton. However, both disulphide bonds and ionic interactions appear to contribute to nuclear complexes containing NA. In addition, NA can be cross-linked within host nuclei with protein cross-linking reagents. The foregoing properties represent current information available for the development of strategies to isolate and characterize these proteins and to investigate host proteins with which NA interact. 

Deprotect the acetylated —SH groups as needed by adding 100 pi of 0.5 M hydroxy-lamine hydrochloride in 50 mM sodium phosphate, 25 mM EDTA, pH 7.5, to each ml of the SATA-modified protein solution. 

Figure 1.65 SATP reacts with amine-containing proteins or other molecules via its NHS ester end to create protected sulfhydryl derivatives in a manner similar to that of SATA. Deprotection can be done with hydroxy-lamine to free the thiol.

To eliminate acylation products at tyrosine residues, add 1 pi of 15 M hydroxy-lamine solution in water to each protein sample and incubate for 30 minutes at 37°C (Zappacosta et al., 2006). 

Not all neurons have NFs. Indeed, one entire phylum in the animal kingdom, arthropods, expresses only type V nuclear lamins so arthropod cells have no IF cytoskeletal structures at all. In addition, mature oligodendrocytes lack IFs although their embryonic precursors contain vimentin. Clearly, the IFs are not essential for cell survival. Yet, in large myelinated fibers, NFs make up the bulk of axonal volume and represent a substantial fraction of the total protein in brain. In most organisms, IFs in both glia... 

Ataxia telangiectasia mutated (ATM), poly(ADP ribose) polymerase (PARP), DNA-dependent protein kinase, DNA replication factor C, DNA topoisomerase I, DNA fragmentation factor (DFF)45, inhibitor of caspase-activated DNAse (ICAD), lamins A, Bl, and C TRAF-1, Rafl, Ras, GAP, GDP dissociation inhibitor of Rho family GTPases, phospholipase A2, Statl... 

For parallel permeation pathways within a single layer of such a laminate, the total permeability may be calculated as the sum of the permeabilities [49], For example, when assuming that permeation may occur through both a lipid fraction and a protein fraction of the stratum corneum, the total permeability is calculated according to Eq. 34 ... 

Caspase-mediated cleavage of specific substrates can explain several of the characteristic features of apoptosis. For example, cleavage of the nuclear lamins and cytoplasmic proteins such as fodrin and gelsolin are required for nuclear and cellular... 

Several farnesylated nuclear proteins have been identified. The nuclear lamins A, B, and C function in the assembly and reorganization of the nu-... 

Examples of proteins that are specifically phosphorylated during the cell cycle are the lamins. Hyperphosphorylation of the lamins leads to disintegration of the nuclear lamina. Myosin in actin-myosin filaments is also specifically phosphorylated during mitosis. Other M-phase-specific phosphorylations occur at transcription factor TFIIIB, leading to inhibition of transcription by RNA polymerase III. Phosphorylation of TAP proteins (see 1.4.2.3) is also involved in general inhibition of banscription. 

Addition of Isoprenyl Groups A number of eukaryotic proteins are modified by the addition of groups derived from isoprene (isoprenyl groups). A thioether bond is formed between the isoprenyl group and a Cys residue of the protein (see Fig. 11-14). The isoprenyl groups are derived from pyrophosphorylated intermediates of the cholesterol biosynthetic pathway (see Fig. 21-33), such as famesyl pyrophosphate (Fig. 27-30). Proteins modified in this way include the Ras proteins, products of the ras oncogenes and proto-oncogenes, and G proteins (both discussed in Chapter 12), and lamins, pro-... 

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