This family consists of several NifT/FixU bacterial proteins. NifT/FixU is a very small, conserved protein that is found in nif clusters; however, its function is unknown [1]. Although it is thought that the protein may be involved in biosynthesis of the FeMo cofactor of nitrogenase although perturbation of nifT expression in K. pneumoniae has only a limited effect on nitrogen fixation [2].

1: Regulation of Three Nitrogenase Gene Clusters in the Cyanobacterium Anabaena variabilis ATCC 29413. Thiel T, Pratte BS; Life (Basel). 2014;4:944-967. PMID:25513762

2: The NifA-RpoN regulon of Mesorhizobium loti strain R7A and its symbiotic activation by a novel LacI/GalR-family regulator. Sullivan JT, Brown SD, Ronson CW; PLoS One. 2013;8:e53762. PMID:23308282