Article Abstract:
The germinal centre kinase (GCK), a human STE20 homologue, has the ability to activate the mammalian stress-activated protein kinase (SAPK) pathway. SAPKs, protein kinases of the ERK type, are activated in situ by inflammatory stimuli and they in turn are probably responsible for stimulating the transactivation function of c-Jun(super 5-7). The activation of SAPK pathway by GCK demonstrates the conservation mechanism of the eukaryotic signalling process and also reveals the physiological function of a mammalian Ste20.
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Article Abstract:
The mitogen-activated protein (MAP) kinase can be catalyzed into a related form, MAP kinase-kinase (MAPK-K), which takes part in developing v-raf-transformed cells, raf being a transforming oncogene. MAPK-K can be rendered inactive by phosphatase 2A; c-Raf-1, a protooncogene product, can restore MAPK-K to the active state. These findings show that c-Raf-1 is an immediate upstream activator of MAPK-K and that MAPK-K is the first physiological substrate of a protooncogene product to be discovered.
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Article Abstract:
Ras regulation of Raf kinase activity depends on the c-Raf CR 1 domain. Raf-1 and Ras can bind directly in vitro and in situ. Test results imply that the active Ras polypeptide targets the c-Raf-1 kinase. The Ras protein appears to regulate the activation state of a set of cytoplasmic protein Ser/Thr kinases. The c-Raf cysteine finger's role suggests that homologous domains in other proteins may enable those proteins to interact directly with Ras.
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