PDBsum entry 2dql

Circadian clock protein

PDB id: 2dql

Contents

Protein chains

115 a.a. *

Ligands

PO4

Waters ×386

* Residue conservation analysis

PDB id:

2dql

Name:

Circadian clock protein

Title:

Crystal structure of the circadian clock associated protein pex from anabaena

Structure:

Pex protein. Chain: a, b. Engineered: yes

Source:

Anabaena sp. Pcc 7120. Organism_taxid: 103690. Strain: pcc7120. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

1.70Å R-factor: 0.234 R-free: 0.255

Authors:

S.Kurosawa,T.Kouyama

Key ref:

S.Kurosawa et al. (2009). Functionally important structural elements of the cyanobacterial clock-related protein Pex. Genes Cells, 14, 1-16. PubMed id: 19032344

Date:

29-May-06 Release date: 29-May-07

Protein chains

Q8YQ56  (Q8YQ56_NOSS1) -  Pex protein from Nostoc sp. (strain PCC 7120 / SAG 25.82 / UTEX 2576)

Seq: 115 a.a.

Struc: 115 a.a.

Enzyme reactions

• Enzyme class: E.C.?

Genes Cells 14:1-16 (2009)

PubMed id: 19032344

Functionally important structural elements of the cyanobacterial clock-related protein Pex.

S.Kurosawa, R.Murakami, K.Onai, M.Morishita, D.Hasegawa, R.Iwase, T.Uzumaki, F.Hayashi, T.Kitajima-Ihara, S.Sakata, M.Murakami, T.Kouyama, M.Ishiura.

ABSTRACT

Pex, a clock-related protein involved in the input pathway of the cyanobacterial circadian clock system, suppresses the expression of clock gene kaiA and lengthens the circadian period. Here, we determined the crystal structure of Anabaena Pex (AnaPex; Anabaena sp. strain PCC 7120) and Synechococcus Pex (SynPex; Synechococcus sp. strain PCC 7942). Pex is a homodimer that forms a winged-helix structure. Using the DNase I protection and electrophoresis mobility shift assays on a Synechococcus kaiA upstream region, we identified a minimal 25-bp sequence that contained an imperfectly inverted repeat sequence as the Pex-binding sequence. Based on crystal structure, we predicted the amino acid residues essential for Pex's DNA-binding activity and examined the effects of various Ala-substitutions in the alpha3 helix and wing region of Pex on in vitro DNA-binding activity and in vivo rhythm functions. Mutant AnaPex proteins carrying a substitution in the wing region displayed no specific DNA-binding activity, whereas those carrying a substitution in the alpha3 helix did display specific binding activity. But the latter were less thermostable than wild-type AnaPex and their in vitro functions were defective. We concluded that Pex binds a kaiA upstream DNA sequence via its wing region and that its alpha3 helix is probably important to its stability.