8TH2

Structure of the isoflavene-forming dirigent protein PsPTS2

Summary for 8TH2

• Entry DOI: 10.2210/pdb8th2/pdb
• Descriptor: Dirigent protein (2 entities in total)
• Functional Keywords: dirigent protein, isoflavene, lignan, pterocarpan, aromatic diterpenoids, plant protein
• Biological source: Pisum sativum (garden pea)
• Total number of polymer chains: 6
• Total formula weight: 145400.51

Authors

Smith, C.A.,Meng, Q.,Lewis, N.G.,Davin, L.B. (deposition date: 2023-07-13, release date: 2024-01-31, Last modification date: 2024-02-28)

Primary citation

Meng, Q.,Moinuddin, S.G.A.,Celoy, R.M.,Smith, C.A.,Young, R.P.,Costa, M.A.,Freeman, R.A.,Fukaya, M.,Kim, D.N.,Cort, J.R.,Hawes, M.C.,van Etten, H.D.,Pandey, P.,Chittiboyina, A.G.,Ferreira, D.,Davin, L.B.,Lewis, N.G.
Dirigent isoflavene-forming PsPTS2: 3D structure, stereochemical, and kinetic characterization comparison with pterocarpan-forming PsPTS1 homolog in pea.
J.Biol.Chem., 300:105647-105647, 2024

PubMed Abstract: Pea phytoalexins (-)-maackiain and (+)-pisatin have opposite C6a/C11a configurations, but biosynthetically how this occurs is unknown. Pea dirigent-protein (DP) PsPTS2 generates 7,2'-dihydroxy-4',5'-methylenedioxyisoflav-3-ene (DMDIF), and stereoselectivity toward four possible 7,2'-dihydroxy-4',5'-methylenedioxyisoflavan-4-ol (DMDI) stereoisomers was investigated. Stereoisomer configurations were determined using NMR spectroscopy, electronic circular dichroism, and molecular orbital analyses. PsPTS2 efficiently converted cis-(3R,4R)-DMDI into DMDIF 20-fold faster than the trans-(3R,4S)-isomer. The 4R-configured substrate's near β-axial OH orientation significantly enhanced its leaving group abilities in generating A-ring mono-quinone methide (QM), whereas 4S-isomer's α-equatorial-OH was a poorer leaving group. Docking simulations indicated that the 4R-configured β-axial OH was closest to Asp, whereas 4S-isomer's α-equatorial OH was further away. Neither cis-(3S,4S)- nor trans-(3S,4R)-DMDIs were substrates, even with the former having C3/C4 stereochemistry as in (+)-pisatin. PsPTS2 used cis-(3R,4R)-7,2'-dihydroxy-4'-methoxyisoflavan-4-ol [cis-(3R,4R)-DMI] and C3/C4 stereoisomers to give 2',7-dihydroxy-4'-methoxyisoflav-3-ene (DMIF). DP homologs may exist in licorice (Glycyrrhiza pallidiflora) and tree legume Bolusanthus speciosus, as DMIF occurs in both species. PsPTS1 utilized cis-(3R,4R)-DMDI to give (-)-maackiain 2200-fold more efficiently than with cis-(3R,4R)-DMI to give (-)-medicarpin. PsPTS1 also slowly converted trans-(3S,4R)-DMDI into (+)-maackiain, reflecting the better 4R configured OH leaving group. PsPTS2 and PsPTS1 provisionally provide the means to enable differing C6a and C11a configurations in (+)-pisatin and (-)-maackiain, via identical DP-engendered mono-QM bound intermediate generation, which PsPTS2 either re-aromatizes to give DMDIF or PsPTS1 intramolecularly cyclizes to afford (-)-maackiain. Substrate docking simulations using PsPTS2 and PsPTS1 indicate cis-(3R,4R)-DMDI binds in the anti-configuration in PsPTS2 to afford DMDIF, and the syn-configuration in PsPTS1 to give maackiain.

PubMed: 38219818
DOI: 10.1016/j.jbc.2024.105647

Experimental method

X-RAY DIFFRACTION (2.6 Å)