The science of… zinc fingers

Zinc fingers might sound like something from science fiction, but they are actually a type of structure found in proteins in lots of different living things. They have important biological roles in the cell and might also be useful in developing ways to treat HIV and other diseases.

Zinc fingers:

• are found in proteins in animals, plants and yeasts
• are a type of protein supersecondary structure, a combination of secondary structures in a 'structural motif'
• fold around zinc atoms bound by cysteine and histidine residues (amino acids) from the protein chain
• bind to DNA, RNA or other proteins, helping the protein interact with other molecules
• are the most common family of transcription factors, proteins that bind DNA to regulate transcription (the process in which the message within DNA is converted into mRNA).

Zinc fingers are being used in research. Using techniques developed by Yen Choo at the Medical Research Council and others, researchers can make zinc fingers to bind to specific sequences of DNA and then combine them with a nuclease domain (a nuclease is an enzyme that can break the phosphodiester bonds between nucleotides in DNA and RNA). The resulting proteins are called zinc finger nucleases.

These artificial 'molecular scissors' can be used to cut DNA strands in specific genes. When the strands are repaired by the cell's machinery, DNA mutations can occur and sometimes result in a non-functioning protein. This is an example of site-specific mutagenesis, a technique that enables researchers to introduce different mutations within genes.

One example of research using zinc finger nucleases is trying to treat HIV infection (see an example). Researchers have created nucleases to disrupt the cell-surface proteins that HIV particles bind to in order to invade the body's CD4 T cells.

Find out more by reading about zinc fingers on the Protein Data Bank website or the Pfam protein families database website, or search for "zinc fingers" online.

This article is part of the online content for ‘Big Picture: Careers From Biology’, which includes an interview with Dr Yen Choo, who helped develop zinc finger nucleases. Download the PDF.

Image: A cartoon representation of a ‘classic zinc finger’. Credit: Jawahar Swaminathan and MSD staff at the European Bioinformatics Institute, via Wikipedia.