3us6

Publication Abstract from PubMed

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 A 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 P21 21 21 symmetry. The protein fold consists of six alpha 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 Kd of 14 mum. DATABASE: The atomic coordinates and structure factors for the crystal structure of histidine-containing phosphotransfer protein MtHPt1 from Medicago truncatula have been deposited with the RCSB Protein Data Bank under the accession code 3us6.

Medicago truncatula histidine-containing phosphotransfer protein: Structural and biochemical insights into the cytokinin transduction pathway in plants.,Ruszkowski M, Brzezinski K, Jedrzejczak R, Dauter M, Dauter Z, Sikorski M, Jaskolski M FEBS J. 2013 Aug;280(15):3709-20. doi: 10.1111/febs.12363. Epub 2013 Jun 24. PMID:23721763^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.