PDBsum entry 4jhh

Plant protein

PDB id: 4jhh

Contents

Protein chain

163 a.a.

Ligands

H35

MLI

Metals

_NA

Waters ×94

PDB id:

4jhh

Name:

Plant protein

Title:

Crystal structure of medicago truncatula nodulin 13 (mtn13) in complex with kinetin

Structure:

Mtn13 protein. Chain: a. Engineered: yes

Source:

Medicago truncatula. Barrel medic. Organism_taxid: 3880. Gene: mtn13. Expressed in: escherichia coli. Expression_system_taxid: 511693.

Resolution:

2.20Å R-factor: 0.188 R-free: 0.215

Authors:

M.Ruszkowski,M.Sikorski,M.Jaskolski

Key ref:

M.Ruszkowski et al. (2013). The landscape of cytokinin binding by a plant nodulin. Acta Crystallogr D Biol Crystallogr, 69, 2365-2380. PubMed id: 24311578 DOI: 10.1107/S0907444913021975

Date:

05-Mar-13 Release date: 04-Dec-13

Protein chain

P93330  (NOD13_MEDTR) -  Nodulin-13 from Medicago truncatula

Seq: 163 a.a.

Struc: 163 a.a.

DOI no: 10.1107/S0907444913021975

Acta Crystallogr D Biol Crystallogr 69:2365-2380 (2013)

PubMed id: 24311578

The landscape of cytokinin binding by a plant nodulin.

M.Ruszkowski, K.Szpotkowski, M.Sikorski, M.Jaskolski.

ABSTRACT

Nodulation is an extraordinary symbiotic interaction between leguminous plants and nitrogen-fixing bacteria (rhizobia) that assimilate atmospheric nitrogen (in root nodules) and convert it into compounds suitable for the plant host. A class of plant hormones called cytokinins are involved in the nodulation process. In the model legume Medicago truncatula, nodulin 13 (MtN13), which belongs to the pathogenesis-related proteins of class 10 (PR-10), is expressed in the outer cortex of the nodules. In general, PR-10 proteins are small and monomeric and have a characteristic fold with an internal hydrophobic cavity formed between a seven-stranded antiparallel β-sheet and a C-terminal α-helix. Previously, some PR-10 proteins not related to nodulation were found to bind cytokinins such as trans-zeatin. Here, four crystal structures of the MtN13 protein are reported in complexes with several cytokinins, namely trans-zeatin, N(6)-isopentenyladenine, kinetin and N(6)-benzyladenine. All four phytohormones are bound in the hydrophobic cavity in the same manner and have excellent definition in the electron-density maps. The binding of the cytokinins appears to be strong and specific and is reinforced by several hydrogen bonds. Although the binding stoichiometry is 1:1, the complex is actually dimeric, with a cytokinin molecule bound in each subunit. The ligand-binding site in each cavity is formed with the participation of a loop element from the other subunit, which plugs the only entrance to the cavity. Interestingly, a homodimer of MtN13 is also formed in solution, as confirmed by small-angle X-ray scattering (SAXS).