SMC complex unidirectionally translocates DNA by coupling segment capture with an asymmetric kleisin path.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Structural maintenance of chromosomes (SMC) complexes are crucial ring-shaped motors for genome folding.
• The precise mechanism of DNA translocation coupled with ATP-driven conformational changes remains unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying SMC complex action on DNA.
• To investigate the role of ATP hydrolysis in SMC-mediated DNA translocation.

Main Methods:

• All-atom and coarse-grained molecular dynamics simulations were employed.
• A near-atomic model of a prokaryotic SMC-kleisin complex was constructed.
• ATP-dependent conformational changes and protein-DNA interactions were incorporated.

Main Results:

• Unidirectional DNA translocation by the SMC complex was observed over an 800 base pair DNA segment.
• The translocation process exhibited a step size of approximately 200 base pairs.
• Kleisin ring asymmetry was identified as a critical factor for unidirectional translocation.

Conclusions:

• SMC complexes capture and pump DNA segments in an ATP-dependent manner.
• The study clarifies the mechanism of SMC-mediated DNA translocation and its implications for genome organization.