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Title: Structure of an intermediate conformer of the spindle checkpoint protein Mad2

The spindle checkpoint senses unattached kinetochores during prometaphase and inhibits the anaphase-promoting complex or cyclosome (APC/C), thus ensuring accurate chromosome segregation. The checkpoint protein mitotic arrest deficient 2 (Mad2) is an unusual protein with multiple folded states. Mad2 adopts the closed conformation (C-Mad2) in a Mad1–Mad2 core complex. In mitosis, kinetochore-bound Mad1–C-Mad2 recruits latent, open Mad2 (O-Mad2) from the cytosol and converts it to an intermediate conformer (I-Mad2), which can then bind and inhibit the APC/C activator cell division cycle 20 (Cdc20) as C-Mad2. In this paper, we report the crystal structure and NMR analysis of I-Mad2 bound to C-Mad2. Although I-Mad2 retains the O-Mad2 fold in crystal and in solution, its core structural elements undergo discernible rigid-body movements and more closely resemble C-Mad2. Residues exhibiting methyl chemical shift changes in I-Mad2 form a contiguous, interior network that connects its C-Mad2–binding site to the conformationally malleable C-terminal region. Mutations of residues at the I-Mad2–C-Mad2 interface hinder I-Mad2 formation and impede the structural transition of Mad2. Finally, our study provides insight into the conformational activation of Mad2 and establishes the basis of allosteric communication between two distal sites in Mad2.
 [1] ;  [2] ;  [1] ;  [3] ;  [1]
  1. Univ. of Texas Southwestern Medical Center, Dallas, TX (United States). Dept. of Pharmacology
  2. Univ. of Texas Southwestern Medical Center, Dallas, TX (United States). Dept. of Biochemistry
  3. Univ. of Texas Southwestern Medical Center, Dallas, TX (United States). Dept. of Pharmacology. Howard Hughes Medical Inst.
Publication Date:
Grant/Contract Number:
AC02-06CH11357; S10RR026461-01; I-1441; GM107415
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 112; Journal Issue: 36; Journal ID: ISSN 0027-8424
National Academy of Sciences, Washington, DC (United States)
Research Org:
Univ. of Texas Southwestern Medical Center, Dallas, TX (United States)
Sponsoring Org:
USDOE; National Inst. of Health (NIH) (United States); Welch Foundation (United States)
Country of Publication:
United States
60 APPLIED LIFE SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; mitosis; conformational change; allostery; NMR; X-ray crystallography
OSTI Identifier: