Catalyzes the reversible dehydration of (R)-homocitrate to cis-homoaconitate, a step in the alpha-aminoadipate pathway for lysine biosynthesis. (2R)-homocitrate = cis-homoaconitate + H2O Binds 1 [4Fe-4S] cluster per subunit. Amino-acid biosynthesis; L-lysine biosynthesis via AAA pathway; L-alpha-aminoadipate from 2-oxoglutarate: step 2/5. Belongs to the aconitase/IPM isomerase family.