4I98: Crystal Structure Of The Complex Between Scpa(residues 1-160)- Scpb(residues 1-183)

Eukaryotic structural maintenance of chromosomes (SMC)-kleisin complexes form large, ring-shaped assemblies that promote accurate chromosome segregation. Their asymmetric structural core comprises SMC heterodimers that associate with both ends of a kleisin subunit. However, prokaryotic condensin Smc-ScpAB is composed of symmetric Smc homodimers associated with the kleisin ScpA in a postulated symmetrical manner. Here, we demonstrate that Smc molecules have two distinct binding sites for ScpA. The N terminus of ScpA binds the Smc coiled coil, whereas the C terminus binds the Smc ATPase domain. We show that in Bacillus subtilis cells, an Smc dimer is bridged by a single ScpAB to generate asymmetric tripartite rings analogous to eukaryotic SMC complexes. We define a molecular mechanism that ensures asymmetric assembly, and we conclude that the basic architecture of SMC-kleisin rings evolved before the emergence of eukaryotes.
PDB ID: 4I98Download
MMDB ID: 107203
PDB Deposition Date: 2012/12/5
Updated in MMDB: 2014/12
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 4I98: trimeric; determined by author and by software (PISA)
Molecular Components in 4I98
Label Count Molecule
Proteins (3 molecules)
Segregation and Condensation Protein a
Molecule annotation
Segregation and Condensation Protein B
Molecule annotation
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Citing MMDB