Estrogen Receptor Protein Beta

The steroid hormones act by regulating genetic activity. The hormone binds to a receptor protein, which is then carried to the nucleus, where it binds to a specific response element on the chromosome. There are two estrogen receptor genes in the human genome, alpha and beta. The music is based on the smaller beta receptor protein. The beta receptor gene is located on human chromosome 14. There are three functional domains in the protein, indicated in the table below: the modulator region, the DNA binding region and the steroid binding region. The DNA binding region is composed of two "zinc fingers". When the protein binds to DNA, the zinc fingers grasp the DNA helix. This protein may form either homodimers or heterodimers with Estrogen Receptor Alpha.

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Notes on the Music:

The piece is set with a reduced scale -- only 11 tones to represent the 20 amino acids. Amino acids with similar solubility properties have been assigned the same pitch. Also running throughout the music is a series of three-note elements representing DNA corresponding to the protein. The protein string is represented by a series of instrumental dyads. In each a legato section played by strings or winds represents the amino acids of lower or medium solubility. The high solubility amino acids punctuate each section with periodic percussive tones in a variety of bell voices.

The three domains of the protein are marked by changes in the instruments, although instrumental changes also occur within a domain. The modulating domain gradually fades in over the background of DNA triplets and begins with mellow horns -- a voice that recurs throughout the piece. The modulating domain is divided into three sections, with the horns bracketing a section containing repetitive percussive sounds. The two zinc fingers of the DNA binding domain are represented by strings, with cymbals marking the cysteines within each finger. Finally the long steroid-binding domain is represented by several different sets of instruments. The piece begins and ends with a series of DNA triplets.

This piece was composed using BankStep sequencing software from Algorithmic Arts, and was created specifically for a student who did a research project on environmental estrogens.