Protein–metabolite interaction network of mammalian and Arabidopsis START domains. (A) Cytoscape was used to visualize the normalized protein–metabolite enrichment data in an edge-weighted interaction network where metabolite interactions held in common by the Arabidopsis START domains were grouped to produce a single node labeled `Plant’, and common interactions for mouse and human proteins (StAR, StARD182L* and PCTP) were grouped to produce a `Mammal’ node. Distances between protein and metabolite nodes reflect the interaction strengths based on the magnitude of the fold-change; the shorter the edge the more enriched the metabolite. The network was filtered for interactions with a greater than tenfold change in enrichment relative to the GV control and only high confidence metabolite assignments were included. If a node had multiple interactions with the same chemical sub-class of metabolite (e.g. PtCho) these interactions were combined and weighted to give one interaction. Asterisks designate metabolites that were validated by mass spectrometry, matching exact mass and retention time to a known standard. (B) Schematic illustrating how START domains may modulate transcription factor activity in plants and mammals. In plants, the START domain is found in HD-Zip transcription factors that contain an HD DNA binding domain. In mammals, the START domain and the DNA binding domains are in two separate proteins. A physical interaction between the START protein PCTP and Pax3 transcription factor comprising both paired box (PAX) and HD DNA binding domains was been reported . GV, GAL4 DNA binding domain:VP16 activation domain; HD, homeodomain; PCTP, phosphatidylcholine transfer protein; PtCho, phosphatidylcholine; SAD, START adjacent domain; StAR, steroidogenic acute regulatory protein; START, StAR-related lipid transfer; Zip, leucine zipper; ZLZ, Zip-Loop-Zipper (a plant-specific leucine zipper).