For chromosome condensation and segregation, most prokaryotic organisms depend on the multi-subunit complex called Smc-ScpAB condensin that consists of a SMC (Structural maintenance of chromosome) protein and two non-SMC subunits ScpA and ScpB. The Smc subunit, which form a homodimer, is characterized by having an ATPase head domain and a hinge domain separated by a ~50 nm-long coiled coil. How condensin complex manipulate DNA fiber is still mysterious. In order to understand the underlying molecular mechanism, we sought to determine the structure of the Smc-ScpAB condensin. By determining 7 different regions of this complex, we were able to reconstitute the structure of full-length Smc and its interaction with ScpAB. Based on these structural analyses, I will discuss ATP-driven mechano-chemical cycle that results in chromosome capture and chromosome loop formation.