... superfamily. The NrdI fam-ily is not divided into short- and long-chain subfami-lies: the region in and around the final strand b5,where the insertion defining the long-chain Fldsoccurs, is extremely highly ... complex,although the flavin N1-C2-O2 atoms would remaininaccessible to residues from NrdF in the complex,unless NrdF induces a conformational change in the 90sloop to expose the flavin. We have identified the ... sequences vary in length from 103 to 188 aminoacids. Intriguingly, one of the most variable loops in NrdI is the one that interacts with the flavin ring ofFMN, namely the 40s loop. In the baNrdI...