Naturally occurring protein kinase

Very large Serine/Threonine kinases and the molecular Target of Rapamycin, a naturally occurring secondary metabolite, TOR proteins function within multiprotein complexes to couple cell growth and stress responses to environmental and developmental cues. 

Fig. 7.2. Structure and substrate binding sites of Ser/Thr-spedfic protein kinases, a) Peptide binding site structure of the catalytic subunit of the cAMP-dependent protein kinase A from mouse, with bound inhibitor peptide PKI (5-22), shown in dark in the figure. PKI (5-22) is a fragment (amino adds 5-22) of the naturally occurring heat-stable protein kinase inhibitor PKI. The inhibitor peptide binds in the region of the substrate binding site between the two lobes of protein kinase A (Knighton et al., 1991). The P-loop is involved in binding the phosphate residue of ATP. b) ATP binding site structure of casein kinase I with bound Mg-ATP. The Mg is shown as a sphere. MOLSKRIPT representation according to Kraulis, (1991).

After PMA treatment the recovery of protein kinase C in the homogenate is 100% when compared to the control homogenate. However, a redistribution of protein kinase C has occurred. Upon activation of protein kinase C by PMA (or by its natural activators DAG and Ca2+ ions) protein kinase C is translocated to the plasma membrane where it phosphorylates protein targets. 

Many opium-derived and other IQs are psychoactive, the best known being the analgesic, addictive, narcotic, opium-derived morphinan alkaloids codeine and morphine (heroin being the semi-synthetic diacetate of morphine). The tertiary or quaternary amine structural component is important for the activity of some Erytkrina alkaloids and bisbenzyliso-quinolines (notably the major curare component (+)-tubocurarine) as antagonists of the nACh-R involved in neuronal excitation of skeletal muscle. The planar disposition of some polycyclic benzophenanthridines enables intercalation (parallel interleaving) between the base pairs of DNA. A variety of naturally occurring and synthetic IQ compounds are protein kinase inhibitors. 

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