cohesin complex 14S cohesin 9S cohesin A protein complex that is required for sister chromatid cohesion in eukaryotes. The cohesin complex forms a molecular ring complex, and is composed of structural maintenance of chromosomes (SMC) and kleisin proteins. For example, in yeast, the complex is composed of the SMC proteins Smc1p and Smc3p, and the kleisin protein Scc1p. In vertebrates, the complex is composed of the SMC1 (SMC1A or SMC1B) and SMC3 heterodimer attached via their hinge domains to a kleisin (RAD21, REC8 or RAD21L) which links them, and one STAG protein (STAG1, STAG2 or STAG3). GO:0008278 GO:0008279 GO:0008280 GO:0043222 SMC complex SMC/kleisin ring complex Smc1-Smc3 complex cellular_component cohesin core heterodimer go.owl pro.owl protein complex chromosomal part