Protein domain

A protein domain is a distinguishable structural and functional region of a protein. A catalytic protein domain and a binding protein domain can carry out different tasks within one chain.

A protein structural motif stabilized by zinc coordination. Different zinc-finger families can bind DNA, RNA or proteins; the motif alone does not establish a transcriptional role.

A DNA-binding protein domain encoded by a homeobox, typically about 60 amino acids long.

A carbohydrate-binding module targets an associated protein to a carbohydrate substrate. Surface enrichment can help insoluble-substrate catalysis, but binding alone does not establish productive access.

A helix-turn-helix is a structural DNA-binding motif in which an intervening turn relates two helices, one often contributing major-groove recognition contacts. The motif alone does not specify which DNA sequence is recognized.

An activation domain is a protein region that promotes transcription when appropriately recruited, often through cofactor interactions. Tethering experiments can distinguish activation capacity from the sequence specificity supplied by a DNA-binding domain.

A DNA-binding domain is a region of a protein contributing to DNA recognition or binding. Its binding specificity can be separable from an activation domain, allowing experimental tests of recognition and transcriptional stimulation.

A protein domain that can recognize particular methylated histone states, with specificity depending on the particular protein.

An SH2 domain is a protein domain that recognizes a phosphotyrosine residue together with surrounding sequence features. This selective binding recruits a protein to a modified receptor or docking protein; it does not itself imply catalysis.^[ref]