Kinetics, regulated proteins

Figure 3.6 Typical kinetics of regulated proteins following neurotrophin treatment of SYSY-TrkA or SYSY-TrkB. The majority of proteins like for instance galectin-1 were regulated in the late stimulation phase. Circles (control) and triangles (neurotrophin-treated) represent single standardized...

Luker KE, Smith MC, Luker GD, Gammon ST, Piwnica-Worms H, Piwnica-Worms D. Kinetics of regulated protein-protein interactions revealed with firefly luciferase complementation imaging in cells and living animals. Proc. Natl. Acad. Sci. U.S.A. 2004 101 12288-12293. 

The contractile apparatus may be thought of as the sum of those intracellular components which constitute the machinery of chemomechanical transduction. It is the set of proteins which convert the chemical energy of the terminal phosphate ester bond of ATP into mechanical work. The structure of the contractile apparatus is determined by the connections between the various protein molecules via specific binding sites or, in a minority of cases, via labile covalent linkages. The kinetics of the contractile machinery are determined by the regulation of changes in these connections. 

Figure 37-14. Alternative promoter use in the liver and pancreatic B cell glucokinase genes. Differential regulation of the glucokinase GK) gene is accomplished by the use of tissue-specific promoters. The B cell GK gene promoter and exon 1B are located about 30 kbp upstream from the liver promoter and exon 1L. Each promoter has a unique structure and is regulated differently. Exons 2-10 are identical in the two genes, and the GK proteins encoded by the liver and B cell mRNAs have identical kinetic properties.

Although the structure of the hydroxylase is now reasonably well understood, less is known about the interactions among the three component proteins of MMO. Despite the fact that the physical properties of the M. capsulatus (Bath) and M. trichosporium OB3b hydroxylases are very similar, preliminary work with the other components indicates that significant differences exist. The manner in which the component proteins interact is quite complex, as manifested by the regulation of electron transfer to the hydroxylase, the product yields and regioselec-tivity of the hydroxylation reaction, and the detailed kinetic behavior of the systems. 

Figure 7.8 Regulation of IRP-1 and IRP-2. The two IRPs are shown as homologous four domain proteins that bind to IREs (left) In iron-replete cells, IRP-1 assembles a cubane Fe-S cluster that is liganded via cys-437, -503 and -506. Similar cysteines are conserved in IRP-2 (Cys-512, -578 and -581), but it is unresolved as to whether they also coordinate an Fe-S cluster, (right) In iron-replete cells, IRP-2 is targeted for destruction via a specific region (shaded in black), whereas IRP-1, with a 4Fe-4S cluster, is stable and active as a cytoplasmic aconitase. Multiple signals induce IRE-binding by IRP-1 with distinct kinetics. Whether or not NO and H2O2 induce IRP-1 by apoprotein formation remains to be addressed directly. From Hentze and Kuhn, 1996. Copyright (1996) National Academy of Sciences, USA.

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