Mitotic checkpoint serine/threonine-protein kinase BUB1 beta (BUB1B)

Required for normal mitosis progression. The mitotic checkpoint delays anaphase until all chromosomes are properly attached to the mitotic spindle.

One of its checkpoint functions would be to inhibit the action of the anaphase-promoting complex/cyclosome (APC/C) by blocking the binding of CDC20 into APC/C, independently of its kinase activity. The other is to monitor kinetochore activities that depend on the kinetochore motor CENPE.