Terminal transferase

Terminal transferase (also known as terminal deoxynucleotidyl transferase or TdT) is a DNA polymerase that is found in immune system cells, specifically lymphocytes, where it plays a crucial role in the immune response.

Function

Terminal transferase is unique among DNA polymerases in that it does not require a template. Instead, it adds nucleotides to the 3' end of a DNA molecule, a process known as nucleotide addition. This is a key step in the creation of antibody diversity, as it allows for the generation of a large number of different antibody molecules from a relatively small number of genes.

Structure

The structure of terminal transferase is complex, with multiple domains and active sites. The enzyme is a monomer, and its active site is located in a deep groove that is lined with amino acid residues. The structure of the enzyme allows it to bind to the end of a DNA molecule and add nucleotides in a template-independent manner.

Clinical significance

Due to its role in the immune system, abnormalities in terminal transferase can lead to immune disorders. For example, a lack of terminal transferase can result in a reduced ability to generate antibody diversity, leading to an increased susceptibility to infection. Conversely, overactivity of terminal transferase can lead to the production of autoantibodies, which can result in autoimmune diseases.

In addition, terminal transferase is often highly expressed in certain types of cancer, particularly leukemia and lymphoma. As such, it is often used as a biomarker in the diagnosis of these diseases.

See also

• DNA polymerase
• Immune system
• Antibody

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