T Box Domain Proteins (TBDs) are a large class of proteins found in all domains of life. TBDs are involved in a variety of functions, including signal transduction, gene transcription and protein-protein interactions. Being involved in such diverse functions, TBDs are essential for the normal functioning of living organisms.

TBDs typically consist of a small peptide of around 200 amino acids. The peptide contains a cysteine-rich T-box element, which is responsible for binding certain DNA segments. This binding allows TBDs to regulate gene expression and thus control the expression of certain proteins.