Sandbox GGC15

Eukaryotic DNA topoisomerase I (topo I) is a protein that reduces the strain from the supercoils that are caused during transcription and translation^[1]. There are two types of topoisomerases. Type 1 topoisomerases are monomeric and break one strand of DNA^[2]. Type 2 topoisomerases are dimeric, meaning that they made up of two units and break both strands of the DNA helix^[2]. They are able to pass another part of the duplex through the cut, and close the cut using ATP^[1].

Structure

Human topo 1 is composed of 765 amino acids ^[2]. The enzyme consist of 4 regions which are the NH2-terminal, core, linker, and COOH-terminal domains^[2]. The NH2-terminal is approximately 210 residues long, it is highly charged, disordered, and contains few hydrophobic amino acids^[2]. The COOH-terminal domain is made up of residues 713 to 765 and contains the important amino aside Tyrosine 223^[2]. The location of the active site is at this amino acid^[2].

Active Site

Topo1 reduces stress in DNA by causing breaks in the DNA helix The active site is catalytic and forms a phosphoester bond with the 3' phosphate at the site of cleavage on the DNA strand^[2].

Relevance

Many anticancer drugs target topo 1 enzymes.

Structural highlights

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