EVIDENCE FOR NUCLEAR-PROTEIN BINDING OF FLAVONOL SULFATE ESTERS IN FLAVERIA-CHLORAEFOLIA

The analysis of isolated nuclei from Flaveria chloraefolia leaves reve aled the association of flavonol sulfate esters with the nuclear compa rtment, in addition to their presence in the cytoplasm. The presence o f flavonol sulfates in the nuclei of Flaveria leaves, has been confirm ed by immunogold labeling with monospecific polyclonal antibodies, rai sed against quercetin 3,7,4'-trisulfate. A nuclear protein fraction th at specifically binds quercetin 3-sulfate (Q3-S) has been partially pu rified by affinity chromatography on a Q3-S-Sepharose affinity column. The nuclear protein exhibited a strong affinity for Q3-S with a bindi ng constant of 85 nmol L(-1). The putative biological significance of sulfated flavonol nuclear binding is discussed in relation to the well documented roles of flavonoids and of metabolite sulfation in cellula r development.