This domain is functionally uncharacterised. This domain is found at the C-terminal of a family of 4Fe-4S, iron-sulphur cluster binding proteins, including Lactate utilisation protein B (LutB). These proteins have a perfect 4Fe-4S binding motif C-x(2)-C-x(2)-C-x(3)-CP followed by either a perfect or imperfect (the first Cys replaced by Ser) second copy. Members probably bind two 4Fe-4S iron-sulphur clusters. This domain is found in LutB proteins in association with the LUD domain (Pfam:PF02589) and usually Fer4_8 (Pfam:PF13183). The LutABC operon is involved in lactate-utilisation and is essential [1,2].

1: LUD, a new protein domain associated with lactate utilization. Hwang WC, Bakolitsa C, Punta M, Coggill PC, Bateman A, Axelrod HL, Rawlings ND, Sedova M, Peterson SN, Eberhardt RY, Aravind L, Pascual J, Godzik A; BMC Bioinformatics. 2013;14:341. PMID:24274019

2: A widely conserved gene cluster required for lactate utilization in Bacillus subtilis and its involvement in biofilm formation. Chai Y, Kolter R, Losick R; J Bacteriol. 2009;191:2423-2430. PMID:19201793