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PDBsum entry 1nwd

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Binding protein/hydrolase PDB id
1nwd
Jmol
Contents
Protein chains
148 a.a. *
28 a.a. *
Metals
_CA ×4
* Residue conservation analysis

References listed in PDB file
Key reference
Title Structural basis for simultaneous binding of two carboxy-Terminal peptides of plant glutamate decarboxylase to calmodulin.
Authors K.L.Yap, T.Yuan, T.K.Mal, H.J.Vogel, M.Ikura.
Ref. J Mol Biol, 2003, 328, 193-204. [DOI no: 10.1016/S0022-2836(03)00271-7]
PubMed id 12684008
Abstract
Activation of glutamate decarboxylase (GAD) by calcium-bound calmodulin (CaM) is required for normal plant growth through regulation of gamma-aminobutyrate and glutamate metabolism. The interaction of CaM with the C-terminal domain of GAD is believed to induce dimerization of the enzyme, an event implicated for Ca(2+)-dependent enzyme activation. Here, we present the solution structure of CaM in complex with a dimer of peptides derived from the C-terminus of Petunia hybrida GAD. The 23 kDa ternary complex is pseudo-symmetrical with each domain of CaM bound to one of the two antiparallel GAD peptides, which form an X-shape with an interhelical angle of 60 degrees. To accommodate the dimeric helical GAD target, the two domains of CaM adopt an orientation markedly different from that seen in other CaM-target complexes. Although the dimeric GAD domain is much larger than previously studied CaM-binding peptides, the two CaM domains appear closer together and make a number of interdomain contacts not observed in earlier complexes. The present structure of a single CaM molecule interacting with two target peptides provides new evidence for the conformational flexibility of CaM as well as a structural basis for the ability of CaM to activate two enzyme molecules simultaneously.
Figure 3.
Figure 3. The NMR structure of Ca^2+-bound CaM in complex with GADp. (a) Stereo-view of the superposition of 20 energy-minimized structures. The view is along the axis of GAD peptide A. CaM helices are in blue, strands in cyan and calcium ions in yellow. Peptide helices are in magenta. (b) Representative structure of the 20 structures illustrated in (a). (c) Same structure rotated to illustrate its pseudo-symmetric orientation. Calcium ions are indicated with roman numerals.
Figure 4.
Figure 4. The interaction between CaM and GADp. (a) Schematic showing observed peptide-peptide NOEs (brown lines) and peptide-CaM NOEs (interacting CaM residues are boxed). Key interacting residues M481, I482 and W485 of GADp are coloured magenta, green and blue, respectively. Potential pseudo-substrate residues E476 and E480 are shown in cyan. (b) Surface representation of CaM showing the same orientation of peptides as in (a). Hydrophobic residues of CaM are shown in yellow. The peptide backbone ribbons and side-chains are coloured as in (a). For clarity, only GADp residues 472-493 are shown as ribbons. Note that E476 and E480 are both facing away from the CaM surface, suggesting that either residue could serve as a pseudo substrate in the absence of CaM. (c) Closer view of GADp residues interacting with the hydrophobic pockets of CaM. The structure is in the same orientation as in Figure 3(a) and (b).
The above figures are reprinted by permission from Elsevier: J Mol Biol (2003, 328, 193-204) copyright 2003.
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