page_title: SMC1A
section_title: Structure
hierarchical_section_title: SMC1A / Structure
caption_attribution_description: English: Structure of the interface between SMC3 (blue) and SMC1 (green) (PDB 2WD5) from mice (Kurze et al. 2009)
context_page_description: Structural maintenance of chromosomes protein 1A is a protein that in humans is encoded by the SMC1A gene. SMC1A is a subunit of the cohesin complex which mediates sister chromatid cohesion, homologous recombination and DNA looping. In somatic cells, cohesin is formed of SMC1A, SMC3, RAD21 and either SA1 or SA2 whereas in meiosis, cohesin is formed of SMC3, SMC1B, REC8 and SA3.
  SMC1A is a member of the SMC protein family. Members of this family are key regulators of DNA repair, chromosome condensation and chromosome segregation from bacteria to humans.
context_section_description: The domain organisation of SMC proteins is highly conserved and is composed of an N-terminal Walker A motif, coiled-coil, "hinge", coiled-coil and a C-terminal Walker B motif. The protein folds back on itself to form a rod-shaped molecule with a heterodimerisation "hinge" domain at one end  and an ABC-type ATPase "head" at the other. These globular domains are separated by a ~50 nm anti-parallel coiled-coil. SMC3 and SMC1 bind via their hinge domains creating V-shaped heterodimers. The N-terminal domain of RAD21 binds to the coiled coil of SMC3 just above the head domain while the C-terminal domain of RAD21 binds the head domain of SMC1. This end to end binding of the SMC3-SMC1-RAD21 trimer creates a closed ring within which DNA can be entrapped.
caption: Structure of the interface between SMC3 (blue) and SMC1 (green) (PDB 2WD5) from mice (Kurze et al. 2009)
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