Apc1 is the largest of the subunits of the anaphase-promoting complex or cyclosome. The anaphase-promoting complex is a multiprotein subunit E3 ubiquitin ligase complex that controls segregation of chromosomes and exit from mitosis in eukaryotes. Apc1 consists of a N-terminal WD40 beta-propeller domain, followed by the middle domain (Mid-N), a PC domain and the C-terminal domain (MidC). This entry represents the middle domain of Apc1, MidN (also referred to as the first helical domain), that coaleses with the C-terminal domain to form Apc1Mid that connects Apc1WD40 with Apc1PC [1,2]. Apc1Mid consists of an alpha-solenoid capped by a beta-sandwich [2].

1: WD40 domain of Apc1 is critical for the coactivator-induced allosteric transition that stimulates APC/C catalytic activity. Li Q, Chang L, Aibara S, Yang J, Zhang Z, Barford D; Proc Natl Acad Sci U S A. 2016;113:10547-10552. PMID:27601667

2: Atomic structure of the APC/C and its mechanism of protein ubiquitination. Chang L, Zhang Z, Yang J, McLaughlin SH, Barford D; Nature. 2015;522:450-454. PMID:26083744