Raf protein

Park et al." used U-4CR libraries to prepare Ras-Raf protein-binding compounds like 30 that are active against HIV. The patented product 31 has been formed by Lockhoft at the Bayer AG using a U-4CR of four different protected glucose derivatives that were later deprotected. The product 32 of... 

Mos/raf protein kinases (see Chapter 9, the mos/raf protein kinases are also involved in signal transduction of growth factors). 

Development of a Yeast Two-Hybrid Screen for Selection of Human Ras-Raf Protein Interaction Inhibitors... 

A yeast two-hybrid screening system was developed to screen for small molecules that inhibit the interaction of the Ras and the Raf proteins. Hyperpermeable yeast strains useful for high-throughput screening (HTS) for the two-hybrid system were created. Differential inhibition of the Ras-Raf vs the hsRPB4-hsRPB7 interaction allowed the identification of selective inhibitors. 

The extract from a laboratory culture of an Indonesian cyanobacterium Phormidium sp. displayed inhibitory activity in a Ras-Raf protein interaction assay. Assay-guided fractionation of the extract led to the isolation of the major inactive metabolite, phormidolide 358 which was nevertheless highly toxic to brine shrimp (LC50 = 1.5 Compound 358 was one of the only few reported macrolide-type natural products, which were obtained from marine cyanobacteria. 

ITC is also applicable to dissect protein-protein interactions. A recent study [47] looked at the energy landscape of Ras/Raf protein-protein interaction with double mutants of the two proteins and ITC. Again, it was noted that... 

Several types of experiments have demonstrated that Raf, MEK, and MAP kinase lie downstream from Ras and have revealed the sequential order of these proteins in the pathway. For example, mutant Raf proteins missing the N-termlnal regulatory domain are constitutively active and Induce quiescent cultured cells to proliferate in the absence of stimulation by growth factors. These mutant Raf proteins were initially identified in tumor cells like the constitutively active Ras° protein, such mutant Raf proteins are said to be encoded by oncogenes (Chapter 23). Conversely, cultured mammalian cells that express a mutant, nonfunctional Raf protein cannot be stimulated to proliferate uncontrollably by a constitutively active Ras° protein. This finding established... 

The MAPK-Dependent Mechanisms. The MAPK-depen-dent mechanisms can be activated by PKC which phosphory-lates the Raf protein, an important kinase of the MARK cascade (1). PLC and PKC can stimulate PGF release by bovine endometrial cells (3), rabbit amnion cells, and hamster ovary cells (9) via the MAPK-dependent pathway. In porcine granulosa cells, the MAPK blocker PD98059 did not affect basal PGF and PGE secretion. Nevertheless, GH, a stimulator of both PGF and PGE, increased the accumulation of MAPK (ERK1,2) in porcine granulosa cells, whereas the MAPK inhibitor PD98059 prevented a stimulatory action of GH on the release of these PG (12). Thus, MAPK can be a mediator of GH action on PG release, but the involvement of MAPK in basal PG secretion should not be excluded. 

Baljuls A, Beck M, Oenel A, Robubi A, Kroschewski R, Hekman M, Rudel T, Rapp UR. The tumor suppressor DiRas3 forms a complex with H-Ras and C-RAF proteins and regulates localization, dimerization, and kinase activity of C-RAF. J Biol Chem. 2012 287 23128 0. 

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