Regulates the expression of the fruBKA (fru) operon, which encodes proteins involved in the import and metabolism of fructose (PubMed:33476373, PubMed:33649152). In the absence of fructose 1-phosphate (F1P), binds to the promoter region of fruB, interferes with the binding of the RNA polymerase (RNAP) to the promoter and represses the expression of the operon (PubMed:33476373, PubMed:33649152). In the presence of F1P, activates the transcription of the fru operon by facilitating the binding of RNAP to the promoter (PubMed:33476373). Essential for the expression of the fru operon and thus for growth on fructose (PubMed:33476373). Interaction with F1P may induce a structural change in the DNA spacer region between the -35 and -10 elements, thereby facilitating RNAP binding to the promoter to trigger the transcriptional activation of the fru operon. Interaction with F1P does not release FruR from its binding sequence. Homodimer. Expressed at the highest levels in fructose media (PubMed:33476373, PubMed:33649152). Expression can be modulated by CRP in the presence of fructose and glucose (PubMed:33649152). Does not affect growth on glucose. Mutant shows a severe growth defect on fructose (PubMed:33476373). In the absence of the gene, expression of the fru genes increases in glucose medium (PubMed:33649152).