InterPro domain: IPR027120

Structural maintenance of chromosomes protein 2 (Smc2) is a central component of the condensin complex, which is 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 [ 1 , 2 , 3 , 4 ].

Amino-acid sequence homology of SMC proteins between species is largely confined to the amino- and carboxy-terminal globular domains. The amino-terminal domain contains a 'Walker A' nucleotide-binding domain (GxxGxGKS/T, in the single-letter amino-acid code), which by mutational studies has been shown to be essential in several proteins. The carboxy-terminal domain contains a sequence (the DA-box) that resembles a 'Walker B' motif, and a motif with homology to the signature sequence of the ATP-binding cassette (ABC) family of ATPases [ 5 , 6 ].

1. Chromosome condensation by a human condensin complex in Xenopus egg extracts. J. Biol. Chem. 276, 5417-20
2. Phosphorylation and activation of 13S condensin by Cdc2 in vitro. Science 282, 487-90
3. 13S condensin actively reconfigures DNA by introducing global positive writhe: implications for chromosome condensation. Cell 98, 239-48
4. MIX-1: an essential component of the C. elegans mitotic machinery executes X chromosome dosage compensation. Cell 92, 265-77
5. A common mechanism for ATP hydrolysis in ABC transporter and helicase superfamilies. Trends Biochem. Sci. 26, 539-44
6. The human ATP-binding cassette (ABC) transporter superfamily. Genome Res. 11, 1156-66