We cloned and characterized a unique and highly compartmentalized sea cucumber aromatization gene, cDNA was 2 036 bp in length, and contained a 1 530 bp open reading frame (ORF), a 250 bp 3′UTR, and a 256 bp 5′UTR. Based on the effective length of gene translation, the full-length cDNA had ATTTA special sequences in the 3′ UTR and polyA regions. The full-length cDNA encoded 509 amino acids constituting a 57.6 kD protein molecule with an isoelectric point of 5.5. The precursor protein was hydrophilic. The protein sequence had one signal peptide, consisting of a 25 amino acid residue. The signal peptide consisted primarily of an alpha helix. The sequence of amino acids contained one transmembrane region, involving in electronic transfer catalysis between the internal and external membrane. We found a single N-glycosylation site, suggesting the precursor protein belonged to the family of secretion transmembrane glycoproteins. The secondary structure of the precursor protein consisted primarily of an alpha helix, with irregular coiling and a strand chain, but without β folding in the complete protein. Sequence comparison revealed that the similarity of theprecursor protein ranged from 35% to 41% with other aquatic animals. We conducted a phylogenetic analysis using the neighbor joining (NJ) method. The evolutionary tree indicated that the P450c17 precursor protein contained a P450 specific structutermed the , a four-helix bundle, helices J and K, and two sets of beta-sheets. These constitute the haem-binding loop (with an absolutely conserved cysteine that serves as the 5th ligand for the haem iron), the proton-transfer groove, and the absolutely conserved EXXR motif in helix K. Our results provide a reference for investigating the function of this; gene cloning; bioinformatics analysis