Structural maintenance of chromosomes (SMC) proteins are
critical regulators of chromosome organization and function (1).
This family of chromosomal ATPases is highly conserved from
bacteria and archaeal species to vertebrates. There are at least
six eukaryotic SMC proteins. The SMC proteins display a common
primary architecture that consists of five structural domains.
The five domains include two nucleotide-binding motifs termed
the Walker A and Walker B motifs located at the N- and
C-terminus, a central “hinge” domain, and two coiled-coil motifs
that flank the central “hinge”. The SMC proteins associate in
specific dimer pairs and arrange in an anti-parallel, two-armed
structure that folds into a V-shape at the “hinge” domain. Three
SMC complexes have been identified and are defined by the SMC
subunits which associate to form a heterodimer and their
respective associated proteins. SMC1 and SMC3 are part of the
cohesin holocomplex which also includes at least two non-SMC
subunits Scc1/mcd1/rad21 and scc3/SA