2E1N

Crystal structure of the Cyanobacterium circadian clock modifier Pex

Summary for 2E1N

• Entry DOI: 10.2210/pdb2e1n/pdb
• Descriptor: Pex, SULFATE ION (3 entities in total)
• Functional Keywords: circadian clock, dna binding protein, circadian clock protein
• Biological source: Synechococcus elongatus PCC 7942
• Total number of polymer chains: 2
• Total formula weight: 32540.48

Authors

Arita, K.,Shimizu, T. (deposition date: 2006-10-26, release date: 2006-11-28, Last modification date: 2024-03-13)

Primary citation

Arita, K.,Hashimoto, H.,Igari, K.,Akaboshi, M.,Kutsuna, S.,Sato, M.,Shimizu, T.
Structural and Biochemical Characterization of a Cyanobacterium Circadian Clock-modifier Protein
J.Biol.Chem., 282:1128-1135, 2007

PubMed Abstract: Circadian clocks are self-sustained biochemical oscillators. The oscillator of cyanobacteria comprises the products of three kai genes (kaiA, kaiB, and kaiC). The autophosphorylation cycle of KaiC oscillates robustly in the cell with a 24-h period and is essential for the basic timing of the cyanobacterial circadian clock. Recently, period extender (pex), mutants of which show a short period phenotype, was classified as a resetting-related gene. In fact, pex mRNA and the pex protein (Pex) increase during the dark period, and a pex mutant subjected to diurnal light-dark cycles shows a 3-h advance in rhythm phase. Here, we report the x-ray crystallographic analysis and biochemical characterization of Pex from cyanobacterium Synechococcus elongatus PCC 7942. The molecule has an (alpha+beta) structure with a winged-helix motif and is indicated to function as a dimer. The subunit arrangement in the dimer is unique and has not been seen in other winged-helix proteins. Electrophoresis mobility shift assay using a 25-base pair complementary oligonucleotide incorporating the kaiA upstream sequence demonstrates that Pex has an affinity for the double-stranded DNA. Furthermore, mutation analysis shows that Pex uses the wing region to recognize the DNA. The in vivo rhythm assay of Pex shows that the constitutive expression of the pex gene harboring the mutation that fails to bind to DNA lacks the period-prolongation activity in the pex-deficient Synechococcus, suggesting that Pex is a DNA-binding transcription factor.

PubMed: 17098741
DOI: 10.1074/jbc.M608148200

Experimental method

X-RAY DIFFRACTION (1.8 Å)