Structural maintenance of chromosomes protein 4 (SMC-4) also known as chromosome-associated polypeptide C (CAP-C) or XCAP-C homolog is a protein that in humans is encoded by the SMC4 gene. SMC-4 is a core subunit of condensin I and II, large protein complexes involved in chromosome condensation

Members of the structural maintenance of chromosomes, or SMC, family (e.g., SMC1A; MIM 300040) are critical for mitotic chromosome condensation in frogs and for DNA repair in mammals.[supplied by OMIM, Nov 2010].
Function: 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.