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Review
. 2023 Jun:80:102598.
doi: 10.1016/j.sbi.2023.102598. Epub 2023 Apr 25.

Structural biology of SMC complexes across the tree of life

Frank Bürmann  1 , Jan Löwe  2
Affiliations
Review

Structural biology of SMC complexes across the tree of life

Frank Bürmann et al. Curr Opin Struct Biol. 2023 Jun.

Abstract

Structural maintenance of chromosomes (SMC) complexes guard and organize the three-dimensional structure of chromosomal DNA across the tree of life. Many SMC functions can be explained by an inherent motor activity that extrudes large DNA loops while the complexes move along their substrate. Here, we review recent structural insights into the architecture and conservation of these molecular machines, their interaction with DNA, and the conformational changes that are linked to their ATP hydrolysis cycle.

Keywords: Chromosome organization; DNA entrapment; DNA loop extrusion; SMC complexes.

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Conflict of interest statement

Conflict of interest statement Nothing declared.

Figures

Figure 1
Figure 1
(a) DNA loop extrusion by an SMC complex. (b) Subunit composition and basic architecture of SMC complexes. The schematic is shown in the familiar “open ring” representation. (c) Cryo-EM structures of HAWK- and KITE-based SMC complexes in their ATP/DNA-free apo form. The position of an elbow/coiled-coil discontinuity is marked with a black arrowhead.
Figure 2
Figure 2
(a) Comparison of kleisin chains. (b) The schematic architecture of HAWK and KITE complexes, with kleisin regions coloured as in A. (c) Comparison of DNA clamped structures. Flexible loop regions not resolved are indicated as black segments. Unresolved arms and hinges are shown as schematics. (d) DNA compartments observed by structural methods.
Figure 3
Figure 3
(a) Tentative loop formation by dimeric SMC complexes. (b) Dimers of SMC complexes as observed by cryo-EM. Dimerization can be mediated by the kleisin (MukBEF and MksBEF/Wadjet), or by the coiled-coil arms (Rad50–Mre11). Note that the different arrangements position the KITEs on the front of the dimer (MukBEF), or both front and back (MksBEF/Wadjet). Rad50–Mre11 is distantly related to SMC complexes and does not contain KITEs/HAWKs/kleisins. Dashed lines and black double lines indicate missing density and shortening of the displayed region, respectively.
See this image and copyright information in PMC

References

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