Molecular Genetics and Genomics

, Volume 273, Issue 2, pp 115–122 | Cite as

Characterization of a mitochondrially targeted single-stranded DNA-binding protein in Arabidopsis thaliana

  • Andrew C. Edmondson
  • Daqing Song
  • Luis A. Alvarez
  • Melisa K. Wall
  • David Almond
  • David A. McClellan
  • Anthony Maxwell
  • Brent L. NielsenEmail author
Original Paper


A gene encoding a predicted mitochondrially targeted single-stranded DNA binding protein (mtSSB) was identified in the Arabidopsis thaliana genome sequence. This gene (At4g11060) codes for a protein of 201 amino acids, including a 28-residue putative mitochondrial targeting transit peptide. Protein sequence alignment shows high similarity between the mtSSB protein and single-stranded DNA binding proteins (SSB) from bacteria, including residues conserved for SSB function. Phylogenetic analysis indicates a close relationship between this protein and other mitochondrially targeted SSB proteins. The predicted targeting sequence was fused with the GFP coding region, and the organellar localization of the expressed fusion protein was determined. Specific targeting to mitochondria was observed in in-vitro import experiments and by transient expression of a GFP fusion construct in Arabidopsis leaves after microprojectile bombardment. The mature mtSSB coding region was overexpressed in Escherichia coli and the protein was purified for biochemical characterization. The purified protein binds single-stranded, but not double-stranded, DNA. MtSSB stimulates the homologous strand-exchange activity of E. coli RecA. These results indicate that mtSSB is a functional homologue of the E. coli SSB, and that it may play a role in mitochondrial DNA recombination.


Single-stranded DNA binding protein (SSB) RecA Homologous recombination 



This work was supported by a grant from the National Institutes of Health and a BYU Mentoring Environment Grant Program award to BLN, and by a BYU Office of Research and Creative Activities Scholarship to ACE. Work by MKW and AM was supported by a grant from the BBSRC (UK). We thank Dr. Fayaz Khazi for early discussions that helped initiate this project and David Sloan for assistance with some experiments.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Andrew C. Edmondson
    • 1
  • Daqing Song
    • 1
  • Luis A. Alvarez
    • 1
  • Melisa K. Wall
    • 3
  • David Almond
    • 2
  • David A. McClellan
    • 2
  • Anthony Maxwell
    • 3
  • Brent L. Nielsen
    • 1
    Email author
  1. 1.Department of Microbiology and Molecular BiologyBrigham Young UniversityProvoUSA
  2. 2.Department of Integrative BiologyBrigham Young UniversityProvoUSA
  3. 3.Department of Biological ChemistryJohn Innes CentreNorwichUK

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