Multiple sequence alignment. Alignment of full-length Steap1, Steap2, Steap3, Steap4, Archaeoglobus fulgidus FNO, and the transmembrane region corresponding to amino acids 207 to 390 of S cerevisiae FRE1. Regions of high homology are boxed, and similar amino acids are depicted in bold. Predicted transmembrane domains of Steap family members are highlighted with solid bars. The Rossman fold motif, GXGXXA/G, is indicated by a series of asterisks. The predicted NAD(P)H binding motif is indicated by dashes. Conserved histidine residues predicted to be involved in heme binding are underlined in transmembrane domains 3 and 5.