Novel interaction of selenium-binding protein with glyceraldehyde-3-phosphate dehydrogenase and fructose-bisphosphate aldolase of Arabidopsis thaliana

The metabolic role and regulation of selenium, particularly in plants, is poorly understood. One of the proteins probably involved in the metabolic regulation of this element is the selenium-binding protein (SBP) with homologues present across prokaryotic and eukaryotic species. The high degree of conservation of SBP in different organisms suggests that this protein may play a role in fundamental biological processes. In order to gain insight into the biochemical function of SBP in plants we used the yeast two-hybrid system to identify proteins that potentially interact with an Arabidopsis thaliana (L.) Heynh. homologue. Among the putative binding partners of SBP, a NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a fructose-bisphosphate aldolase (FBA) were found as reliable positive candidates. The interaction of these proteins with SBP was confirmed by in vitro binding assays. Previous findings in Escherichia coli, demonstrated the direct binding of selenium to both GAPDH and aldolase. Therefore our results reveal the interaction, at least in pairs, of three proteins that are possibly linked to selenium and suggest the existence of a protein network consisting of at least SBP, GAPDH and FBA, triggered by or regulating selenium metabolism in plant cells.