title: Trimeric structure of (+)-pinoresinol-forming dirigent protein at 1.95 Å resolution with three isolated active sites.
abstract: 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. DPs are involved in lignan biosynthesis, whereas dirigent domains/sites have been implicated in lignin deposition.
authors.affiliation: From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340.
authors.forename: Kye-Won
authors.initials: KW
authors.lastname: Kim
authors.affiliation: the Stanford Synchrotron Radiation Lightsource, Menlo Park, California 94025, and.
authors.forename: Clyde A
authors.initials: CA
authors.lastname: Smith
authors.affiliation: the Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Daily
authors.affiliation: the Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354.
authors.forename: John R
authors.initials: JR
authors.lastname: Cort
authors.affiliation: From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340.
authors.forename: Laurence B
authors.initials: LB
authors.lastname: Davin
authors.affiliation: From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340, lewisn@wsu.edu.
authors.forename: Norman G
authors.initials: NG
authors.lastname: Lewis
mesh_terms: D000438:Alcohols / Q000737:chemistry; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D005663:Furans / Q000737:chemistry*; D017705:Lignans / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000737:chemistry / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry*; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000438:Alcohols; D005663:Furans; D017705:Lignans; D010940:Plant Proteins; D008031:Lignin; C103298:pinoresinol
keywords: Crystallography; Dirigent Proteins; Homology Modeling; Molecular Docking; Phenoxy Radical Radical Coupling; Protein Crystallization; Secondary Metabolism