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Molecular mechanism of Mad1 kinetochore targeting by phosphorylated Bub1

DOI: 10.15252/embr.202052242 DOI Help

Authors: Elyse S. Fischer (MRC Laboratory of Molecular Biology) , Conny W. H. Yu (MRC Laboratory of Molecular Biology) , Dom Bellini (MRC Laboratory of Molecular Biology) , Stephen H. Mclaughlin (MRC Laboratory of Molecular Biology) , Christian Orr (Diamond Light Source) , Armin Wagner (Diamond Light Source) , Stefan M. V. Freund (MRC Laboratory of Molecular Biology) , David Barford (MRC Laboratory of Molecular Biology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Embo Reports , VOL 536

State: Published (Approved)
Published: May 2021

Open Access Open Access

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 (Mad1CTD) bound to two phosphorylated Bub1CD1 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 Bub1CD1 peptide binds to the Mad1 homodimer in solution. We suggest that this stoichiometry is due to inherent asymmetry in the coiled-coil of Mad1CTD and has implications for how the Mad1-Bub1 complex at kinetochores promotes efficient MCC assembly.

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I04-Macromolecular Crystallography , I23-Long wavelength MX

Added On: 21/05/2021 21:15

Discipline Tags:

Biochemistry Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX) Long Wavelength Crystallography