Dictyostelium discoideum phosphorylation

These studies demonstrate the general mechanism of synchronization of biochemical systems, which I expect to be operative in even more complex systems, such as the mitochondrial respiration or the periodic activity of the slime mold Dictyostelium discoideum. As shown in a number of laboratories under suitable conditions mitochondrial respiration can break into self-sustained oscillations of ATP and ADP, NADH, cytochromes, and oxygen uptake as well as various ion transport and proton transport functions. It is important to note that mitochondrial respiration and oxidative phosphorylation under conditions of oscillations is open for the source, namely, oxygen, as well as with respect to a number of sink reactions producing water, carbon dioxide, and heat. 

The chemotactic response to cAMP of the slime mould Dictyostelium discoideum is presented as an example. When these cells are starving, they sense cAMP signals, and in response to the hunger signal, cAMP, the cells differentiate (reviewed in ref. 67). In Dictyostelium discoideum the response to cAMP is mediated by G-protein-coupled hepta-helical receptors and is transmitted by the Py subunits of a heterotrimeric G protein. In response to the chemoattractant, cAMP, a homologue of PKB (protein kinase B) is rapidly activated by phosphorylation througji a Ptdins kinase specific for the 3-OH position (see also Chapter 4). 

In the slime mould, Dictyostelium discoideum, a STAT-like DNA-binding protein, DIF (the differentiation-inducing factor), is expressed. DIF is about 700 amino-acid residues long, and has substantial homology with mammalian STATs. DIF is, like STAT, activated by phosphorylation of tyrosines. It is essential for differentiation of the stalk cells of D. discoideum A The long evolutionary path that the STATs have travelled from Dictyostelium to mammals underlines their conserved and essential role as signal transmitters and transcriptional activators in early development. 

Meier, K. C. Klein, 1988. An unusual protein kinase phosphorylates the chemotactic receptor in Dictyostelium discoideum. Proc. Natl. Acad. ScL USA 85 2181-5. 

Vaughan, R. P.N. Devreotes. 1988. Ligand-induced phosphorylation of the cAMP receptor from Dictyostelium discoideum. J. BioL Chem. 

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