This domain is found in checkpoint proteins which are involved in cell division. This region has been shown to be necessary and sufficient for the binding of MAD3 to BUB3 in Saccharomyces cerevisiae. This domain is present in BUB1 which also binds BUB3 [1].

1: MAD3 encodes a novel component of the spindle checkpoint which interacts with Bub3p, Cdc20p, and Mad2p. Hardwick KG, Johnston RC, Smith DL, Murray AW; J Cell Biol 2000;148:871-882. PMID:10704439