Central component of the condensin complex, a complex required for conversion of interphase chromatin into mitotic-like condense chromosomes. The condensin complex probably introduces positive supercoils into relaxed DNA in the presence of type I topoisomerases and converts nicked DNA into positive knotted forms in the presence of type II topoisomerases. Also involved in chromosome segregation in meiosis. Forms a heterodimer with a SMC2 subfamily member. Component of the condensin complex, which contains the SMC2 and SMC4 heterodimer, and three non SMC subunits that probably regulate the complex: CAPH, CAPD2 and CAPG. Associates with chromatin. A number of isoforms are produced. According to EST sequences. Highly expressed in seedlings and inflorescences. The SMC hinge domain, which separates the large intramolecular coiled coil regions, allows the heterodimerization with a SMC2 subfamily member, forming a V-shaped heterodimer. Belongs to the SMC family. SMC4 subfamily.