passages.id: split_5_test_1480_passage
passages.type: progene_text
passages.text: Mutation of either Tyr(456) , which makes van der Waals contact with the FAD isoalloxazine ring and also hydrogen - bonds to the ribityl 4 ' - hydroxyl , or Arg(454) , which bonds to the FAD pyrophosphate , decreases the affinity for FAD 8000 - and 25 , 000 - fold , respectively , with corresponding decreases in cytochrome c reductase activity .