Protein importance

The maturation of the precursor protein involves their proteolytic cleavage. There are two proteins important in this cleavage, so-called processing protease and protease enhancing peptide. These are now believed to be nonidentical subunits of the same enzyme. The structural requirements for recognition of the cleavage site are not fully understood and except for a positively charged residue at position (-2) there is no consensus sequence around this site. 

Fujiki, M. Vemer, K. (1993). Coupling of cytosolic protein synthesis and mitochondrial protein import in yeast. J. Biol. Chem. 268, 1914-1920. 

Manning-Krieg, U.C., Scherer, P.E., Schatz, G. (1991), Sequential action of mitochondrial chaperon-ins in protein import into the matrix. EMBO J. 10,3273-3280. 

Pfanner, N., Rossow, J., van der Klei, I.J., Neupert W. (1992). A dynamic model of the mitochondrial protein import machinery. Cell 68,999-1002. 

While the majority of reported work concerning the sequencing of biomolecules by LC-MS has involved proteins, important information may also be obtained from oligosaccharides by employing a similar methodology to that described previously. 

TaWe 46-1. Some general features of protein import to organelles. ... 

The pathways of protein import into mitochondria, nuclei, peroxisomes, and the endoplasmic reticulum are described. 

Adam, SA., Marr, R. S., and Gerace, L. (1990). Nuclear protein import in permeabilized mammalian cells requires soluble cytoplasmic factors. J. Cell Biol. Ill, 807—816. 

Finally, this section has focused almost entirely on axonal transport, but dendritic transport also occurs [25]. Since dendrites usually include postsynaptic regions while most axons terminate in presynaptic elements, the dendritic and axonal transport each receive a number of unique proteins. An added level of complexity for intraneuronal transport phenomena is the intriguing observation that mRNA is routed into dendrites where it is implicated in local protein synthesis at postsynaptic sites, but ribosomal components and mRNA are largely excluded from axonal domains [26]. Regulation of protein synthesis in dendritic compartments is an important mechanism is synaptic plasticity [27,28]. The importance of dendritic mRNA transport and local protein synthesis is underscored by the demonstration that the mutation associated with Fragile X syndrome affects a protein important for transport and localization of mRNA in dendrites [27, 29], Similar processes of mRNA transport have been described in glial cells [30]. 

Matrix protein import after docking ZS, NALD, IRD 3... 

SchnellDJ, KesslerF, BlobelG. Isolation of components ofthe chloroplast protein import machinery. Science 1994 266 1007-1012. 

A variety of protein import pathways into the vacuole are known (Burd et al., 1998 Bryant and Stevens, 1998). It includes the sorting from the Golgi apparatus, endocytosis, autophagy (where a part of the cytoplasm such as a mitochondrion is engulfed into a newly formed vacuole and is degraded), direct import from the cytosol, and the vacuolar inheritance from the mother cell. Of these, the pathways from the Golgi... 

Chen, X., and Schnell, D. (1999). Protein import into chloroplasts. Trends Cell Biol. 9, 222-227. 

Crookes, W., and Olsen, L. (1999). Peroxin puzzles and folded freight peroxisomal protein import in review. Naturwissenschaften 86, 51-61. 

Hicks, G., and Raikhel, N. (1995). Protein import into the nucleus an integrated view. Annu. Rev. Cell Dev. Biol. 11, 55-88. 

Neupert, W. (1997). Protein import into mitochondria. Annu. Rev. Biochem. 66, 863-917. 

Schatz, G. (1996). The protein import system of mitochondria./. Biol. Chem. 271, 31763-31766. 

M. Miiller, Proteolysis in Protein Import and Export Signal Peptide Processing in Eu-and Prokaryotes , Experientia 1992, 48, 118-129. 

N. Pfanner, W. Neupert, The Mitochondrial Protein Import Apparatus , Annu. Rev. Biochem. 1990, 59, 331-353. 

UbclO is required for the biogenesis of the peroxisome, an oxidative organelle [75]. This E2 plays a role in peroxisomal protein import [76] and is recruited to the peroxisomal membrane through an interaction with a partner protein [77]. Membrane-localized UbclO also seems to be spatially proximal to PexlO, which has a RING-like domain [78]. Whether PexlO is a cognate E3 of UbclO remains to be determined, as does the mechanistic role of ubiquitin conjugation in peroxisome biogenesis. 

K N., Wenzel, T. J., Rangell, L, Keller, G. A., and Subramani, S. Pex22p of Pichia pastoris, essential for peroxisomal matrix protein import, anchors the ubiquitin-conjugating enzyme, Pex4p, on the peroxisomal membrane. J. Cell Biol. 1999, 346, 99-112. 

Eckert, J. H. and Johnsson, N. PexlOp links the ubiquitin conjugating enzyme Pex4p to the protein import machinery of the peroxisome. J. Cell Sci. 2003, 336, 3623-34. 

Wing, J. P., et al., Drosophila Morgue is an F box/ubiquitin conjugase domain protein important for grim-reaper mediated apoptosis. Nat Cell Biol, 2002, 4(6), 451-6. 

The same regions appear to be important for interactions of ubiquitin with many other DUBs (see Figure 8.2) and Ub-binding proteins. Importantly, all ubiquitin-binding domains examined utilize these same surfaces in binding ubiquitin. 

Based on the intrinsic mitochondriotropism of dequalinium and its unique self-assembly behavior, we have developed a strategy for direct mitochondrial transfection (47-49), which involves the transport of a DNA-mitochondrial leader sequence (MLS) peptide conjugate to mitochondria using DQAsomes, the liberation of this conjugate from the cationic vector upon contact with the mitochondrial outer membrane followed by DNA uptake via the mitochondrial protein import machinery. We have demonstrated that DQAsomes fulfill all essential prerequisites for a mitochondria-specific DNA delivery system they bind and condense pDNA (24), protect it from... 

Bradley PJ, Lahti CJ, Plumper E, Johnsons PJ. 1997. Targeting and translocation of proteins into the hydrogenosome of the protist Trichomonas similarities with mitochondrial protein import. EMBO J 16 3484-93. 

K Carboxylation of glutamic acid residues in many Ca +-binding proteins, importantly coagulation factors II, VII, EX, and X, as well as protein C and protein S... 

Fig. 2. Macroscopic and microscopic structure of muscle (a) Entire muscle and its cross-section with fatty septa, (b) Fascicle with several muscle fibres (cells). A layer of fat along the fascicle is indicated, (c) Striated myofibre corresponding with one single muscle cell containing several nuclei. The lengths of a myofibre can be several tens of centimetres, (d) Myofibril inside a myocyte. It is one contractile element and contains actin and myosin and further proteins important for the muscular function, (e) Electron myograph of human skeletal muscle showing the band structure caused by the contractile myofilaments in the sarcomeres. One nucleus (Nu) and small glycogen granules (arrow, size <0.1 pm) are indicated.

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