Member of a network of 50S ribosomal subunit biogenesis factors (ObgE, RluD, RsfS and DarP(YjgA)) which assembles along the 30S-50S interface, preventing incorrect 23S rRNA structures from forming. Binds to late stage, pre-50S ribosomal subunits where it contacts ObgE and enhances the latter's GTPase activity. Addition to isolated ribosomal subunits partially inhibits their association, preventing translation