passages.id: split_4_validation_879_passage
passages.type: progene_text
passages.text: We found previously that FNR binds to a site centred at position - 41.5 at the nir promoter , but that FNR - dependent activation is repressed by IHF binding to a site centred at position - 88 ( IHF I ) and Fis binding to sites centred at positions - 142 ( Fis I ) and + 23 ( Fis II ) .