Involved in the erythromycin biosynthesis pathway. Acts by forming a complex and stabilizing the desosaminyl transferase EryCIII. Antibiotic biosynthesis; erythromycin biosynthesis. Heterotetramer composed of EryCII and EryCIII. Belongs to the cytochrome P450 family. Although related to the cytochrome P450 family, lacks the heme-binding sites.