PDBsum entry 1xj6

Signaling protein, transferase

PDB id: 1xj6

Contents

Protein chains

105 a.a. *

Ligands

HEM ×2

Metals

_CL ×2

_NA ×2

Waters ×102

* Residue conservation analysis

PDB id:

1xj6

Name:

Signaling protein, transferase

Title:

Structure of bjfixlh in the unliganded ferrous form

Structure:

Sensor protein fixl. Chain: a, b. Fragment: heme domain. Synonym: bjfixlh fixl. Engineered: yes. Other_details: unliganded

Source:

Bradyrhizobium japonicum. Organism_taxid: 375. Gene: fixl. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PQS)

Resolution:

1.90Å R-factor: 0.207 R-free: 0.247

Authors:

J.Key,K.Moffat

Key ref:

J.Key and K.Moffat (2005). Crystal structures of deoxy and CO-bound bjFixLH reveal details of ligand recognition and signaling. Biochemistry, 44, 4627-4635. PubMed id: 15779889 DOI: 10.1021/bi047942r

Date:

22-Sep-04 Release date: 29-Mar-05

Protein chains

P23222  (FIXL_BRADU) -  Sensor protein FixL from Bradyrhizobium diazoefficiens (strain JCM 10833 / BCRC 13528 / IAM 13628 / NBRC 14792 / USDA 110)

Seq: 505 a.a.

Struc: 105 a.a.

Enzyme reactions

• Enzyme class: E.C.2.7.13.3 - histidine kinase.
• Reaction: ATP + protein L-histidine = ADP + protein N-phospho-L-histidine

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1021/bi047942r

Biochemistry 44:4627-4635 (2005)

PubMed id: 15779889

Crystal structures of deoxy and CO-bound bjFixLH reveal details of ligand recognition and signaling.

J.Key, K.Moffat.

ABSTRACT

Rhizobia directly regulate the expression of genes required for symbiotic nitrogen fixation in response to oxygen concentration via the sensor protein FixL. The N-terminal PAS domain of FixL contains a histidine-coordinated heme and regulates the activity of its effector domain, a C-terminal histidine kinase, in response to binding of oxygen and other ligands at the heme. To further investigate ligand-induced inhibition of FixL, we have determined the crystal structures of the heme domain in both the deoxy state and bound to carbon monoxide, a weak inhibitor of FixL kinase activity. Structures collected at room temperature are presented in each state from two crystallographic space groups at 1.8 and 2 A resolution. These structures reveal displacement of the residues of the H(beta) and I(beta) strands by Leu236 upon CO binding, and this structural change propagates more than 15 A to a region of the structure implicated in signal transduction in PAS proteins. Displacement of residues Ile215, Ile216, and Gly217 in the FG loop is also evident, accompanied by the movement of heme propionate 6 upon change in iron ligation. CO binding increases the temperature factors in the FG loop of the protein and disorders the side chain of Arg206, a conserved residue involved in the FG loop switch mechanism. We relate these results to structural changes in other PAS sensor domains and their involvement in catalytic control.