NblA protein from Synechococcus elongatus PCC 7942

Experimental Data Snapshot

  • Resolution: 2.20 Å
  • R-Value Free: 0.347 
  • R-Value Work: 0.248 

Starting Model: experimental
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Structural, Functional, and Mutational Analysis of the NblA Protein Provides Insight into Possible Modes of Interaction with the Phycobilisome

Dines, M.Sendersky, E.David, L.Schwarz, R.Adir, N.

(2008) J Biol Chem 283: 30330-30340

  • DOI: https://doi.org/10.1074/jbc.M804241200
  • Primary Citation of Related Structures:  
    2Q8V, 2QDO, 3CS5

  • PubMed Abstract: 

    The enormous macromolecular phycobilisome antenna complex (>4 MDa) in cyanobacteria and red algae undergoes controlled degradation during certain forms of nutrient starvation. The NblA protein (approximately 6 kDa) has been identified as an essential component in this process. We have used structural, biochemical, and genetic methods to obtain molecular details on the mode of action of the NblA protein. We have determined the three-dimensional structure of the NblA protein from both the thermophilic cyanobacterium Thermosynechococcus vulcanus and the mesophilic cyanobacterium Synechococcus elongatus sp. PCC 7942. The NblA monomer has a helix-loop-helix motif which dimerizes into an open, four-helical bundle, identical to the previously determined NblA structure from Anabaena. Previous studies indicated that mutations to NblA residues near the C terminus impaired its binding to phycobilisome proteins in vitro, whereas the only mutation known to affect NblA function in vivo is located near the protein N terminus. We performed random mutagenesis of the S. elongatus nblA gene which enabled the identification of four additional amino acids crucial for NblA function in vivo. This data shows that essential amino acids are not confined to the protein termini. We also show that expression of the Anabaena nblA gene complements phycobilisome degradation in an S. elongatus NblA-null mutant despite the low homology between NblAs of these cyanobacteria. We propose that the NblA interacts with the phycobilisome via "structural mimicry" due to similarity in structural motifs found in all phycobiliproteins. This suggestion leads to a new model for the mode of NblA action which involves the entire NblA protein.

  • Organizational Affiliation

    Schulich Faculty of Chemistry and Institute of Catalysis, Science, and Technology, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Phycobilisome degradation protein nblA
A, B, C, D
59Synechococcus elongatus PCC 7942 = FACHB-805Mutation(s): 0 
Gene Names: nblA
Find proteins for P35087 (Synechococcus elongatus (strain ATCC 33912 / PCC 7942 / FACHB-805))
Explore P35087 
Go to UniProtKB:  P35087
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP35087
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.20 Å
  • R-Value Free: 0.347 
  • R-Value Work: 0.248 
  • Space Group: P 4
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 78.08α = 90
b = 78.08β = 90
c = 70.678γ = 90
Software Package:
Software NamePurpose
DNAdata collection
MOSFLMdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-09-09
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2023-11-01
    Changes: Data collection, Database references, Refinement description