Catalyzes the isomerization of citrate to isocitrate via cis-aconitate (PubMed:12438312). Has probably no RNA-binding activity (PubMed:12438312). citrate = D-threo-isocitrate Binds 1 [4Fe-4S] cluster per subunit. Interacts with gex-3. Belongs to the aconitase/IPM isomerase family.