PDBsum entry 1t4z

Transferase

PDB id: 1t4z

Contents

Protein chain

105 a.a. *

* Residue conservation analysis

PDB id:

1t4z

Name:

Transferase

Title:

Solution structure of the n-terminal domain of synechococcus elongatus sasa (25-structures ensemble)

Structure:

Adaptive-response sensory-kinase sasa. Chain: a. Fragment: n-terminal domain. Engineered: yes

Source:

Synechococcus elongatus. Organism_taxid: 1140. Strain: pcc 7942. Gene: sasa, sars. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

NMR struc:

25 models

Authors:

I.Vakonakis,D.A.Klewer,A.C.Liwang

Key ref:

I.Vakonakis et al. (2004). Structure of the N-terminal domain of the circadian clock-associated histidine kinase SasA. J Mol Biol, 342, 9. PubMed id: 15313603 DOI: 10.1016/j.jmb.2004.07.010

Date:

30-Apr-04 Release date: 16-Nov-04

Protein chain

Q06904  (SASA_SYNE7) -  Adaptive-response sensory kinase SasA from Synechococcus elongatus (strain ATCC 33912 / PCC 7942 / FACHB-805)

Seq: 387 a.a.

Struc: 105 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

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: 10.1016/j.jmb.2004.07.010

J Mol Biol 342:9 (2004)

PubMed id: 15313603

Structure of the N-terminal domain of the circadian clock-associated histidine kinase SasA.

I.Vakonakis, D.A.Klewer, S.B.Williams, S.S.Golden, A.C.LiWang.

ABSTRACT

Circadian oscillators are endogenous biological systems that generate the approximately 24 hour temporal pattern of biological processes and confer a reproductive fitness advantage to their hosts. The cyanobacterial clock is the simplest known and the only clock system for which structural information for core component proteins, in this case KaiA, KaiB and KaiC, is available. SasA, a clock-associated histidine kinase, is necessary for robustness of the circadian rhythm of gene expression and implicated in clock output. The N-terminal domain of SasA (N-SasA) interacts directly with KaiC and likely functions as the sensory domain controlling the SasA histidine kinase activity. N-SasA and KaiB share significant sequence similarity and, thus, it has been proposed that they would be structurally similar and may even compete for KaiC binding. Here, we report the NMR structure of N-SasA and show it to be different from that of KaiB. The structural comparisons provide no clear details to suggest competition of SasA and KaiB for KaiC binding. N-SasA adopts a canonical thioredoxin fold but lacks the catalytic cysteine residues. A patch of conserved, solvent-exposed residues is found near the canonical thioredoxin active site. We suggest that this surface is used by N-SasA for protein-protein interactions. Our analysis suggests that the structural differences between N-SasA and KaiB are the result of only a few critical amino acid substitutions.

Selected figure(s)

Figure 2.
Figure 2. Solution structure of the N-SasA domain and comparison to other thioredoxin-fold proteins. Shown here are (A) the average minimized structure of N-SasA and (B) the 25-structure ensemble in two mutually orthogonal views. The N- and C-termini of the protein are indicated. The ensemble of structures was superimposed using the backbone of low-mobility residues (Table 1). (C) Comparison of bacteriophage T4 glutaredoxin (PDB-ID 1AAZ), the N-SasA domain and Escherichia coli thioredoxin (2TRX). The unstructured first ten residues of N-SasA, and the first 20 residues of thioredoxin that have no structural homologues in N-SasA are not shown. The structures were superimposed using the C^a atoms of the b-sheet.

Figure 4.
Figure 4. Structure comparison of the N-SasA domain and KaiB. (A) Shown here is a CLUSTAL-W alignment of S. elongatus N-SasA and KaiB. The secondary structure elements from the solution structure of N-SasA (top line), and the crystal structure of the Anabaena sp. PCC 7120 KaiB8 (highly homologous to S. elongatus KaiB; bottom line) are shown. Residues likely to be critical for the differences in the two structures are indicated by yellow bars. (B) Secondary structure prediction for S. elongatus N-SasA and KaiB. Prediction was performed by PSIPRED36 and the regular secondary structure elements identified are shown. N-SasA residues 1-8 are not shown. (C) Structures and (D) protein architectures of S. elongatus N-SasA and Anabaena sp. KaiB.8 The unstructured first ten residues of N-SasA are not shown. The protein architectures are highly similar for the first half of the sequences but diverge in the second half.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2004, 342, 9-0) copyright 2004.

Figures were selected by the author.