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. Forms an heterodimer with SMC2. Component of the condensin complex, which contains the SMC2 and SMC4 heterodimer, and three non SMC subunits that probably regulate the complex: BRRN1/CAPH, CNAP1/CAPD2 and CAPG. Widely expressed. Higher expression in testis, colon, thymus. Belongs to the SMC family. SMC4 subfamily. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.