Three flavonoids were isolated from dried flowers of Sophora japonica using repetitive column chromatography and high-performance liquid chromatography. The flavonoids were identified as rutin (1), quercetin-3'-O-methyl-3-O-α-L-rhamnopyranosyl(1 → 6)-β-D-glucopyranoside (2), and quercetin (3) on the basis of spectroscopic analysis and comparison of values reported in the literature. These compounds inhibited the action of sortase A (SrtA) from Streptococcus mutans, a primary etiologic agent of human dental caries. The onset and magnitude of inhibition of saliva-induced aggregation of S. mutans treated with compound 1 was comparable to that of untreated S. mutans with a deletion of the srtA gene.
Phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha) is known to be an important translational control mechanism in all eukaryotes with the major exception of plants. Regulation of mammalian and yeast eIF2alpha activity is directly governed by specific phosphorylation on Ser-51. We now demonstrate that recombinant wheat wild-type (51S) but not mutant 51-Ala (51A) protein is phosphorylated by human PKR and yeast GCN2, which are defined eIF2alpha kinases. Further, only wheat wild-type eIF2alpha is a substrate for plant-encoded, double-stranded RNA-dependent kinase (pPKR) activity. Plant PKR and GCN2 phosphorylate recombinant yeast eIF2alpha 51S but not the 51A mutant demonstrating that pPKR has recognition site capability similar to established eIF2alpha kinases. A truncated version of wild-type wheat eIF2alpha containing 51S but not the KGYID motif is not phosphorylated by either hPKR or pPKR suggesting that this putative eIF2alpha kinase docking domain is essential for phosphorylation. Taken together, these results demonstrate the homology among eukaryotic eIF2alpha species and eIF2alpha kinases and support the presence of a plant eIF2alpha phosphorylation pathway.
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