1X3G: Crystal Structure Of The Single-Stranded Dna-Binding Protein From Mycobacterium Smegmatis

The structure of Mycobacterium smegmatis single-stranded DNA-binding protein (SSB) has been determined using three data sets collected from related crystals. The structure is similar to that of its homologue from Mycobacterium tuberculosis, indicating that the clamp arrangement that stabilizes the dimer and the ellipsoidal shape of the tetramer are characteristic features of mycobacterial SSBs. The central OB fold is conserved in mycobacterial SSBs as well as those from Escherichia coli, Deinococcus radiodurans and human mitochondria. However, the quaternary structure exhibits considerable variability. The observed plasticity of the subunit is related to this variability. The crystal structures and modelling provide a rationale for the variability. The strand involved in the clamp mechanism, which leads to higher stability of the tetramer, appears to occur in all high-G+C Gram-positive bacteria. The higher stability is perhaps required by these organisms. The mode of DNA binding of mycobacterial SSBs is different from that of E. coli SSB partly on account of the difference in the shape of the tetramers. Another difference between the two modes is that the former contains additional ionic interactions and is more susceptible to salt concentration.
PDB ID: 1X3GDownload
MMDB ID: 34619
PDB Deposition Date: 2005/5/5
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 3  Å
Source Organism:
Similar Structures:
Biological Unit for 1X3G: tetrameric; determined by author
Molecular Components in 1X3G
Label Count Molecule
Proteins (4 molecules)
Single-strand Binding Protein(Gene symbol: MSMEG_6896)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB