Solution structure of the N-terminal domain of Synechococcus elongatus SasA (25-structures ensemble)

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 25 
  • Selection Criteria: structures with the lowest energy 

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

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

(2004) J Mol Biol 342: 9-17

  • DOI: https://doi.org/10.1016/j.jmb.2004.07.010
  • Primary Citation of Related Structures:  
    1T4Y, 1T4Z

  • PubMed 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.

  • Organizational Affiliation

    Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Adaptive-response sensory-kinase sasA105Synechococcus elongatus PCC 7942 = FACHB-805Mutation(s): 0 
Gene Names: SASASARS
EC: 2.7
Find proteins for Q06904 (Synechococcus elongatus (strain ATCC 33912 / PCC 7942 / FACHB-805))
Explore Q06904 
Go to UniProtKB:  Q06904
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ06904
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 25 
  • Selection Criteria: structures with the lowest energy 

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-11-16
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Source and taxonomy, Version format compliance
  • Version 1.3: 2024-05-01
    Changes: Data collection, Database references