Proteolytic complexes

In the ubiquitin—proteasome pathway, the substrate proteins are marked by covalent linkage to ubiquitin for degradation by a proteolytic complex, the proteasome. 

The term proteasome is used to describe two kinds of multisubunit proteolytic complexes, the 26S and 20S, based on their sedimentation coefficient. The 26S proteasome degrades ubiquitinated protein substrates. The 26S complex contains the 20S as a core and regulatory caps on either end like a dumb bell. Each cap of the 26S proteasome is known as the 19S regulatory complex (19S RC). The 20S core is a cylindrical structure consisting of the catalytic part of the proteasome. ... 

The proteasome is a large multisubunit proteolytic complex that participates in the degradation of proteins critical for cell cycle regulation. The proteasome inhibitors can overcome drug resistance. This effect is thought to be mediated through prevention of activation of NF-kB (nuclear transcription factor-icB) by proteasome inhibition. NF-kB is considered as one of the key factors involved in apoptotic pathways... 

Proteasomes are unusually large multisubunit proteolytic complexes consisting of two primary components (1) a central catalytic machine (equivalent to the 20S proteasome) and (2) two terminal regulatory subcomplexes termed PA700 that are... 

Driscoll,]., and Goldberg, A. L (1990). The proteasomc (multicatalytic protease) is a component of the 1500-kDa proteolytic complex which degrades ubiquitin-conjugated pto-tein.s. /. Biai Cbetn. 265,4789-4792. 

Besides equilibria in the liquid phase (proteolytic, complex forming, etc.) that influence directly the values of effective mobilities of compounds to be separated, it is necessary to also establish, in the electrophoretic system, equilibria between the liquid and solid phase. In electrophoretic techniques which use solid stabilizing media adsorption of solutes on the sorbent surface is the main consideration. In capillary methods, and with colloid particles, similar effects have also to be considered (the surface of the solid phase that is in contact with the liquid phase is, with respect to the volume of the liquid, rather large). In both these latter cases the interaction between the solid and liquid phases participates in the formation of the electric double layer that conditions the electro-osmotic flow, and attributes the electric charge to colloid particles. 

Fig 37.5. The proteasome and cap proteins. The cap proteins (PA700 and PA28) regulate the activity of this proteolytic complex by recruiting to the complex the substrates for proteolysis. The ATP requirement is to unfold and denature the proteins targeted for destruction, although the PA28 protease complex does not require ATP. 

Phytic acid (9), although restricted to a more narrow range of food products, mainly grains, complexes a broader spectmm of minerals than does oxahc acid. Decreased availabiUty of P is probably the most widely recognized result of excessive iatakes of phytic acid, yet Ca, Cu, Zn, Fe, and Mn are also complexed and rendered unavailable by this compound (47—49). Phytic acid has also been reported to reduce the activity of a-amylase and to decrease the activity of both proteolytic and Hpolytic enzymes (50). 

Protein G. This vitamin K-dependent glycoproteia serine protease zymogen is produced ia the Hver. It is an anticoagulant with species specificity (19—21). Proteia C is activated to Proteia by thrombomodulin, a proteia that resides on the surface of endothefial cells, plus thrombin ia the presence of calcium. In its active form, Proteia selectively iaactivates, by proteolytic degradation. Factors V, Va, VIII, and Villa. In this reaction the efficiency of Proteia is enhanced by complex formation with free Proteia S. la additioa, Proteia activates tissue plasminogen activator, which... 

Respiratory sensitizers Isocyanates proteolytic enzymes p-phenylene diamine complex salts of platinum cyanuric chloride. ... 

Therapeutic Function Antiinflammatory Chemical Name Complex proteolytic enzyme Common Name —... 

Apoptotic initiator caspases (caspase-2, -8, -9 and -10) constitute a subgroup of the caspase family. These caspases are the first to become proteolytically active in the apoptotic cascade. Their activation takes place in multiprotein complexes initiated by pro-apoptotic stimuli, such as TNFa, a-Fas, staurosporine. Once activated, they can process their substrates, which include the apoptotic executioner caspases. 

Inflammatory caspases (caspase-1, -4, -5,-11 and -12) constitute a subgroup of the caspase family. Caspase-1 is the best characterized member and is responsible for the proteolytic maturation and release of the pro-inflammatory cytokines pro-interleukin (IL)-1 (3 and pro-IL-18. Caspase-1 gets activated in inflammasome complexes upon cellular stress, cellular damage and infection. 

In mammalia, seven different members encoded by distinct genes have been identified, all of which are activated by a distinct set of cytokines. Diversity in signaling is provided by variants of STAT proteins derived from either alternative splicing of RNA transcripts or proteolytic processing (e.g., STATs 1,3,4, and 5) and the ability of certain STATs to form both homodimers and heterodimers with each other. In response to inteiferon-y monomeric STAT1 dimerizes, while upon interferon-a stimulation a heterotrimeric complex consisting of STAT 1 and STAT2 with associated... 

CarriUo A, Stewart KD, Sham HL, Norbeck DW, Kohlbrenner WE, Leonard JM, Kempf DJ, Molla A (1998) In vitro selection and characterization of human immunodeficiency virus type 1 variants with increased resistance to ABT-378, a novel protease inhibitor. J Virol 72 7532-7541 Chambers TJ, Nestorowicz A, Amberg SM, Rice CM (1993) Mutagenesis of the yellow fever virus NS2B protein effects on proteolytic processing, NS2B-NS3 complex formation, and viral replication. J Virol 67 6797-6807... 

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