Journal of Biological Chemistry291(15),7877–7887(2016), DOI10.1074/jbc.M116.717991. Primary byline Sk Tofajjen Hossain retained exactly; Sk not expanded. Abstract and Figures1–3: designed RNA substrates, S1-domain mutations, ATP binding and intrinsic tryptophan fluorescence used to distinguish nuclease/helicase functions. No claim that helicase activity necessarily hydrolyzes ATP.