3HBX

Crystal structure of GAD1 from Arabidopsis thaliana

Summary for 3HBX

• Entry DOI: 10.2210/pdb3hbx/pdb
• Descriptor: Glutamate decarboxylase 1 (2 entities in total)
• Functional Keywords: calmodulin-binding, decarboxylase, lyase, pyridoxal phosphate
• Biological source: Arabidopsis thaliana (mouse-ear cress,thale-cress)
• Total number of polymer chains: 6
• Total formula weight: 344173.76

Authors

Gut, H.,Dominici, P.,Pilati, S.,Gruetter, M.G.,Capitani, G. (deposition date: 2009-05-05, release date: 2009-07-28, Last modification date: 2023-11-22)

Primary citation

Gut, H.,Dominici, P.,Pilati, S.,Astegno, A.,Petoukhov, M.V.,Svergun, D.I.,Grutter, M.G.,Capitani, G.
A common structural basis for pH- and calmodulin-mediated regulation in plant glutamate decarboxylase.
J.Mol.Biol., 392:334-351, 2009

PubMed Abstract: 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.

PubMed: 19580813
DOI: 10.1016/j.jmb.2009.06.080

Experimental method

X-RAY DIFFRACTION (2.672 Å)