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A Common Structural Basis for pH- and Calmodulin-mediated Regulation in Plant Glutamate Decarboxylase.

Gut, Heinz, Dominici, Paola, Pilati, Stefania, Astegno, Alessandra, Petoukhov, Maxim V, Svergun, Dmitri I, Gruetter, Markus and Capitani, Guido (2009) A Common Structural Basis for pH- and Calmodulin-mediated Regulation in Plant Glutamate Decarboxylase. Journal of Molecular Biology. ISSN 1089-8638


Glutamate decarboxylase (Gad) catalyzes glutamate to gamma-aminobutyrate conversion. Plant Gad is a approximately 340 kDa hexamer, involved in development and stress response, and regulated by pH and binding of Ca(2+)/calmodulin (CaM) to the C-terminal domain. We determined the crystal structure of Arabidopsis thaliana Gad1 in its CaM-free state, obtained a low-resolution structure of the calmodulin-activated Gad complex by small-angle X-ray scattering and identified the crucial residues, in the C-terminal domain, for regulation by pH and CaM binding. CaM activates Gad1 in a unique way by relieving two C-terminal autoinhibition domains of adjacent active sites, forming a 393 kDa Gad1-CaM complex with an unusual 1:3 stoichiometry. The complex is loosely packed: thanks to the flexible linkers connecting the enzyme core with the six C-terminal regulatory domains, the CaM molecules retain considerable positional and orientational freedom with respect to Gad1. The complex thus represents a prototype for a novel CaM-target interaction mode. Thanks to its two levels of regulation, both targeting the C-terminal domain, Gad can respond flexibly to different kinds of cellular stress occurring at different pH values.

Item Type: Article
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Additional Information: author can archive post-print (ie final draft post-refereeing); Publisher's version/PDF cannot be used
Keywords: calmodulin-mediated activation; plant development and stress response; glutamate decarboxylase; pyridoxal 5′-phosphate; protein–protein interactions
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Date Deposited: 14 Dec 2009 13:49
Last Modified: 14 Dec 2009 13:49


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