Superoxide dismutase is an enzyme that converts free oxygen radicals to peroxide and to molecular oxygen. The active enzyme is a homodimer, i.e. it contains two molecules of the same polypeptide. Each polypeptide contains one copper and one zinc ion. The folding pattern is a "Greek key" formed of beta strands. .

The molecule is very widespread, and has been identified in many species from bacteria to humans. Because of its antioxidant activity, the enzyme is a great medical interest. Some cases of familial ALS (Lou Gehrig's disease) have been associated with mutations in this enzyme.

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Cu-Zn Superoxide Dismutase Human ( ) = alpha helix [ ] = beta strand < > = turn

ATK[AVCVLK]GDGPV[QGIINFE]QKESNGPV [KVWG]SIKGLTE[GLHGFHVH] EFGDN<TAGCTSA>GP [H]FNPLSRKHGGPKDEERHVGDL[GNVTA] D(KDG)VAD[VSI]EDSVISLSGDHCI<IG>R[TLVVH] EKADDLGKGGN(EESTKT)GNAGS [RLACGV]I[GI]AQ

Link to the Music: Cu-Zn Superoxide Dismutase

Notes on the Music:

In the music, the 153 amino acid sequence of the protein is played through 3 times. The first read-through is a duet between oboe and flute, playing the more polar (water-soluble) and nonpolar (water-insoluble) amino acids respectively. In the second repetition of the sequence, other instruments represent the regions of secondary structure: trumpets for the beta strands, chimes for alpha helix, and tubular bells for the turns. The remainder of the sequence is played in this section by a harp-string combination of voices. In the final section, the duet between polar and nonpolar voices becomes a trio, with a second oboe playing the polar amino acids using a slightly different scale. Throughout the piece, the DNA sequence accompanies the amino acid sequence as a series of triple beats from a percussion section. This second voice is an allusion to the dimeric form of the active enzyme.