3US6

Crystal Structure of Histidine-containing Phosphotransfer Protein MtHPt1 from Medicago truncatula

Summary for 3US6

• Entry DOI: 10.2210/pdb3us6/pdb
• Related: 1QSP 1WN0 1YVI 2Q4F
• Descriptor: Histidine-containing Phosphotransfer Protein type 1, MtHPt1 (2 entities in total)
• Functional Keywords: helix bundle, plant hormone signal transduction, cytokinin signal transduction, phosphorylation, phosphate transfer relay, response regulator, transferase, signaling protein, cytokinin receptor cre1
• Biological source: Medicago truncatula (Barrel medic)
• Total number of polymer chains: 1
• Total formula weight: 17782.30

Authors

Ruszkowski, M.,Brzezinski, K.,Jedrzejczak, R.,Dauter, M.,Dauter, Z.,Sikorski, M.,Jaskolski, M. (deposition date: 2011-11-23, release date: 2012-01-18, Last modification date: 2023-09-13)

Primary citation

Ruszkowski, M.,Brzezinski, K.,Jedrzejczak, R.,Dauter, M.,Dauter, Z.,Sikorski, M.,Jaskolski, M.
Medicago truncatula histidine-containing phosphotransfer protein: Structural and biochemical insights into the cytokinin transduction pathway in plants.
Febs J., 280:3709-3720, 2013

PubMed Abstract: Histidine-containing phosphotransfer proteins (HPts) take part in hormone signal transduction in higher plants. The overall pathway of this process is reminiscent of the two-component system initially identified in prokaryotes. HPts function in histidine-aspartate phosphorelays in which they mediate the signal from sensory kinases (usually membrane proteins) to RRs in the nucleus. Here, we report the crystal structure of an HPt protein from Medicago truncatula (MtHPt1) determined at 1.45 Å resolution and refined to an R-factor of 16.7% using low-temperature synchrotron-radiation X-ray diffraction data. There is one MtHPt1 molecule in the asymmetric unit of the crystal lattice with P2(1)2(1)2(1) symmetry. The protein fold consists of six α helices, four of which form a C-terminal helix bundle. The coiled-coil structure of the bundle is stabilized by a network of S-aromatic interactions involving highly conserved sulfur-containing residues. The structure reveals a solvent-exposed side chain of His79, which is the phosphorylation site, as demonstrated by autoradiography combined with site-directed mutation. It is surrounded by highly conserved residues present in all plant HPts. These residues form a putative docking interface for either the receiver domain of the sensory kinase, or for the RR. The biological activity of MtHPt1 was tested by autoradiography. It demonstrated phosphorylation by the intracellular kinase domain of the cytokinin receptor MtCRE1. Complex formation between MtHPt1 and the intracellular fragment of MtCRE1 was confirmed by thermophoresis, with a dissociation constant K(d) of 14 μM.

PubMed: 23721763
DOI: 10.1111/febs.12363

Experimental method

X-RAY DIFFRACTION (1.446 Å)