Structural maintenance of chromosomes (SMC) protein complexes, including cohesin 
and condensin, play key roles in the regulation of higher-order chromosome 
organization. Even though SMC proteins are thought to mechanistically determine 
the function of the complexes, their native conformations and dynamics have 
remained unclear. Here, we probe the topology of Smc2-Smc4 dimers of the S. 
cerevisiae condensin complex with high-speed atomic force microscopy (AFM) in 
liquid. We show that the Smc2-Smc4 coiled coils are highly flexible polymers 
with a persistence length of only ∼ 4 nm. Moreover, we demonstrate that the SMC 
dimers can adopt various architectures that interconvert dynamically over time, 
and we find that the SMC head domains engage not only with each other, but also 
with the hinge domain situated at the other end of the ∼ 45-nm-long coiled coil. 
Our findings reveal structural properties that provide insights into the 
molecular mechanics of condensin complexes.