4I99: Crystal Structure Of The Smchead Bound To The C-winged Helix Domain Of Scpa

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: 4I99Download
MMDB ID: 107204
PDB Deposition Date: 2012/12/5
Updated in MMDB: 2017/09
Experimental Method:
x-ray diffraction
Resolution: 2.3  Å
Source Organism:
Similar Structures:
Biological Unit for 4I99: tetrameric; determined by author and by software (PISA)
Molecular Components in 4I99
Label Count Molecule
Proteins (4 molecules)
Chromosome Partition Protein SMC(Gene symbol: PF_RS09310)
Molecule annotation
Putative Uncharacterized Protein
Molecule annotation
Chemicals (3 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB