This domain occurs near the C-terminus of the respiratory nitrate reductase beta chain. The nitrate reductase complex is a dimer of heterotrimers each consisting of an alpha, beta and gamma chain. This domain plays a role in the interactions between subunits and shielding of the Fe-S clusters [1]

1: Insights into the respiratory electron transfer pathway from the structure of nitrate reductase A. Bertero MG, Rothery RA, Palak M, Hou C, Lim D, Blasco F, Weiner JH, Strynadka NC; Nat Struct Biol. 2003;10:681-687. PMID:12910261