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Title: Trimeric Structure of (+)-Pinoresinol-forming Dirigent Protein at 1.95 Å Resolution with Three Isolated Active Sites

Control over phenoxy radical-radical coupling reactions in vivo in vascular plants was enigmatic until our discovery of dirigent proteins (DPs, from the Latin dirigere, to guide or align). The first three-dimensional structure of a DP ((+)-pinoresinol-forming DP, 1.95 Å resolution, rhombohedral space group H32)) is reported herein. It has a tightly packed trimeric structure with an eight-stranded β-barrel topology for each DP monomer. Each putative substrate binding and orientation coupling site is located on the trimer surface but too far apart for intermolecular coupling between sites. It is proposed that each site enables stereoselective coupling (using either two coniferyl alcohol radicals or a radical and a monolignol). Interestingly, there are six differentially conserved residues in DPs affording either the (+)- or (₋)-antipodes in the vicinity of the putative binding site and region known to control stereoselectivity. We find DPs are involved in lignan biosynthesis, whereas dirigent domains/sites have been implicated in lignin deposition.
 [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [1]
  1. Washington State Univ., Pullman, WA (United States). Inst. of Biological Chemistry
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Fundamental and Computational Sciences Directorate
Publication Date:
Grant/Contract Number:
FG-0397ER20259; MCB-1052557
Accepted Manuscript
Journal Name:
Journal of Biological Chemistry
Additional Journal Information:
Journal Volume: 290; Journal Issue: 3; Journal ID: ISSN 0021-9258
American Society for Biochemistry and Molecular Biology
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Crystallography; Homology Modeling; Molecular Docking; Protein Crystallization; Secondary Metabolism; Dirigent Proteins; Phenoxy Radical Radical Coupling
OSTI Identifier: