4Q0K: Crystal Structure Of Phytohormone Binding Protein From Medicago Truncatula In Complex With Gibberellic Acid (ga3)

Pathogenesis-related proteins of class 10 (PR-10) are a family of plant proteins with the same fold characterized by a large hydrophobic cavity that allows them to bind various ligands, such as phytohormones. A subfamily with only approximately 20% sequence identity but with a conserved canonical PR-10 fold have previously been recognized as Cytokinin-Specific Binding Proteins (CSBPs), although structurally the binding mode of trans-zeatin (a cytokinin phytohormone) was found to be quite diversified. Here, it is shown that two CSBP orthologues from Medicago truncatula and Vigna radiata bind gibberellic acid (GA3), which is an entirely different phytohormone, in a conserved and highly specific manner. In both cases a single GA3 molecule is found in the internal cavity of the protein. The structural data derived from high-resolution crystal structures are corroborated by isothermal titration calorimetry (ITC), which reveals a much stronger interaction with GA3 than with trans-zeatin and pH dependence of the binding profile. As a conclusion, it is postulated that the CSBP subfamily of plant PR-10 proteins should be more properly linked with general phytohormone-binding properties and termed phytohormone-binding proteins (PhBP).
PDB ID: 4Q0KDownload
MMDB ID: 120392
PDB Deposition Date: 2014/4/2
Updated in MMDB: 2014/07
Experimental Method:
x-ray diffraction
Resolution: 1.34  Å
Source Organism:
Similar Structures:
Biological Unit for 4Q0K: monomeric; determined by author and by software (PISA)
Molecular Components in 4Q0K
Label Count Molecule
Protein (1 molecule)
Phytohormone Binding Protein Mtphbp(Gene symbol: LOC11418550)
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

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