7B1H

Monoclinic P21 Structure of Human Mad1 C-terminal Domain in Complex with Phosphorylated Bub1 CD1 Domain

Summary for 7B1H

• Entry DOI: 10.2210/pdb7b1h/pdb
• Descriptor: Mitotic spindle assembly checkpoint protein MAD1, Mitotic checkpoint serine/threonine-protein kinase BUB1 (3 entities in total)
• Functional Keywords: mad1, bub1, spindle assembly checkpoint, mitotic checkpoint complex, cell cycle
• Biological source: Homo sapiens (Human); More
• Total number of polymer chains: 8
• Total formula weight: 67940.49

Authors

Fischer, E.,Bellini, D.,Barford, D. (deposition date: 2020-11-24, release date: 2021-03-17, Last modification date: 2024-11-13)

Primary citation

Fischer, E.S.,Yu, C.W.H.,Bellini, D.,McLaughlin, S.H.,Orr, C.M.,Wagner, A.,Freund, S.M.V.,Barford, D.
Molecular mechanism of Mad1 kinetochore targeting by phosphorylated Bub1.
Embo Rep., 22:e52242-e52242, 2021

PubMed Abstract: During metaphase, in response to improper kinetochore-microtubule attachments, the spindle assembly checkpoint (SAC) activates the mitotic checkpoint complex (MCC), an inhibitor of the anaphase-promoting complex/cyclosome (APC/C). This process is orchestrated by the kinase Mps1, which initiates the assembly of the MCC onto kinetochores through a sequential phosphorylation-dependent signalling cascade. The Mad1-Mad2 complex, which is required to catalyse MCC formation, is targeted to kinetochores through a direct interaction with the phosphorylated conserved domain 1 (CD1) of Bub1. Here, we present the crystal structure of the C-terminal domain of Mad1 (Mad1 ) bound to two phosphorylated Bub1 peptides at 1.75 Å resolution. This interaction is mediated by phosphorylated Bub1 Thr461, which not only directly interacts with Arg617 of the Mad1 RLK (Arg-Leu-Lys) motif, but also directly acts as an N-terminal cap to the CD1 α-helix dipole. Surprisingly, only one Bub1 peptide binds to the Mad1 homodimer in solution. We suggest that this stoichiometry is due to inherent asymmetry in the coiled-coil of Mad1 and has implications for how the Mad1-Bub1 complex at kinetochores promotes efficient MCC assembly.

PubMed: 34013668
DOI: 10.15252/embr.202052242

Experimental method

X-RAY DIFFRACTION (2.4 Å)