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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/4615

Title: Allosteric interactions and bifunctionality make the response of glutamine synthetase cascade system of Escherichia coli robust and ultrasensitive
Authors: MUTALIK, VK
SHAH, P
VENKATESH, KV
Keywords: interconvertible enzyme cascades
protein-kinase cascade
signal-transduction
covalent modification
metabolic-regulation
biochemical systems
zero-order
sensitivity
adenylylation
state
Issue Date: 2003
Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Citation: JOURNAL OF BIOLOGICAL CHEMISTRY, 278(29), 26327-26332
Abstract: Glutamine synthetase (GS) regulation in Escherichia coli by reversible covalent modification cycles is a prototype of signal transduction by enzyme cascades. Such enzyme cascades are known to exhibit ultrasensitive response to primary stimuli and act as signal integration systems. Here, we have quantified GS bicyclic cascade based on steady state analysis by evaluating Hill coefficient. We demonstrate that adenylylation of GS with glutamine as input is insensitive to total enzyme concentrations of GS, uridylyltransferase/uridylyl-removing enzyme, regulatory protein PII, and adenylyltransferase/adenylyl-removing enzyme. This robust response of GS adenylylation is also observed for change in system parameters. From numerical analyses, we show that the robust ultrasensitive response of bicyclic cascade is because of allosteric interactions of glutamine and 2-ketoglutarate, bifunctionality of converter enzymes, and closed loop bicyclic cascade structure. By system level quantification of the GS bicyclic cascade, we conclude that such a robust response may help the cell in adapting to different carbon and nitrogen status.
URI: http://dx.doi.org/10.1074/jbc.M300129200
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4615
http://hdl.handle.net/10054/4615
ISSN: 0021-9258
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