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Title: Protein arginine deiminase 2 binds calcium in an ordered fashion: Implications for inhibitor design

Protein arginine deiminases (PADs) are calcium-dependent histone-modifying enzymes whose activity is dysregulated in inflammatory diseases and cancer. PAD2 functions as an Estrogen Receptor (ER) coactivator in breast cancer cells via the citrullination of histone tail arginine residues at ER binding sites. Although an attractive therapeutic target, the mechanisms that regulate PAD2 activity are largely unknown, especially the detailed role of how calcium facilitates enzyme activation. To gain insights into these regulatory processes, we determined the first structures of PAD2 (27 in total), and through calcium-titrations by X-ray crystallography, determined the order of binding and affinity for the six calcium ions that bind and activate this enzyme. These structures also identified several PAD2 regulatory elements, including a calcium switch that controls proper positioning of the catalytic cysteine residue, and a novel active site shielding mechanism. Additional biochemical and mass-spectrometry-based hydrogen/deuterium exchange studies support these structural findings. The identification of multiple intermediate calcium-bound structures along the PAD2 activation pathway provides critical insights that will aid the development of allosteric inhibitors targeting the PADs.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [4] ;  [5] ;  [6] ;  [5] ;  [2] ;  [4] ;  [3]
  1. The Scripps Research Institute, Jupiter, FL (United States); Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States)
  2. The Scripps Research Institute, Jupiter, FL (United States)
  3. The Scripps Research Institute, Jupiter, FL (United States); Univ. of Massachusetts Medical School, Worcester, MA (United States)
  4. Washington Univ. in St. Louis, St. Louis, MO (United States)
  5. GlaxoSmithKline (United Kingdom). Medicines Research Centre.
  6. Cornell Univ., Ithaca, NY (United States)
Publication Date:
OSTI Identifier:
1215427
Grant/Contract Number:
W871XWH-07-0372; GM079357; GM103422
Type:
Accepted Manuscript
Journal Name:
ACS Chemical Biology
Additional Journal Information:
Journal Volume: 10; Journal Issue: 4; Journal ID: ISSN 1554-8929
Publisher:
American Chemical Society
Research Org:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES