PNNL

Abstract

Elucidation of the 3D structures of two stereo-selective pterocarpan-forming dirigent proteins, affording medicarpin from its isoflavonoid precursors, allowed for comparison to stereoselective lignan and aromatic terpenoid forming orthologues. Studies of these dirigent proteins providing entry into diverse plant natural products classes suggest that the common biochemical mechanism is in binding and stabilizing distinct plant phenol-derived mono- and bis-quinone methide intermediates during different C–C and C–O bond forming processes. While the vast majority (>95%) of dirigent proteins in their large multi-gene families awaits discovery of biochemical function, these observations provide key insights into both their appearance and functional diversification during land plant adaptation. Based on the proposed biochemical mechanisms, these data provide important clues as to how additional physiological roles for dirigent proteins can now be rationally and systematically identified.