FIGURE 3.

Alignment of secondary structure for representatives of the NADH oxidase/flavin reductase superfamily. IYD and BluB now define a third subclass of the NADH oxidase/flavin reductase superfamily. NADH oxidase (NOX) and FRP illustrate the α-β fold for the original two subclasses of this superfamily. The boxed regions indicate the sequences that form the active site lids. The dotted lines indicate spacing inserted for alignment. Structural assignments were derived from crystallographic data (Protein Data Bank codes 3GFD, 2ISL, 1NOX, and 2BKJ, respectively).