Architecture of SMC-kleisin complexes

In all cellular systems, the transmission of bulk genetic
information during proliferation occurs in the form of chromosomes.
The segregation of these entities upon cell division is of pivotal
importance for all forms of life. Structural maintenance of
chromosomes (SMC)-kleisin complexes are ubiquitous and essential
factors that ensure proper organisation and segregation of the
genetic material. Aim of this work was to elucidate evolutionary
conserved features in the architecture of SMC-kleisin complexes,
and to probe these features for functional relevance. We find that
two major architectural themes have been constrained by evolution:
(I) SMC-kleisin complexes form asymmetric assemblies with a
ring-like topology, whereby a kleisin monomer bridges two different
binding sites on a SMC dimer, (II) SMC-kleisin complexes form
rod-like structures, whereby the SMC proteins of a given dimer are
closely juxtaposed in a well-defined manner. Based on these
findings, we propose that SMC-kleisin complexes from all domains of
life act by a unifying mechanism.