2X6U

Crystal structure of human TBX5 in the DNA-free form

Summary for 2X6U

• Entry DOI: 10.2210/pdb2x6u/pdb
• Related: 2X6V
• Descriptor: T-BOX TRANSCRIPTION FACTOR TBX5, 2-{2-[2-(2-{2-[2-(2-ETHOXY-ETHOXY)-ETHOXY]-ETHOXY}-ETHOXY)-ETHOXY]-ETHOXY}-ETHANOL, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: developmental protein, dna-binding, holt-oram-syndrome, ig-fold, nuclear protein, repressor, tbx3, transcription, transcription regulation
• Biological source: HOMO SAPIENS (HUMAN)
• Cellular location: Nucleus (Potential): Q99593
• Total number of polymer chains: 1
• Total formula weight: 23857.75

Authors

Stirnimann, C.U.,Mueller, C.W. (deposition date: 2010-02-22, release date: 2010-04-28, Last modification date: 2024-05-08)

Primary citation

Stirnimann, C.U.,Ptchelkine, D.,Grimm, C.,Muller, C.W.
Structural Basis of Tbx5-DNA Recognition: The T-Box Domain in its DNA-Bound and -Unbound Form.
J.Mol.Biol., 400:71-, 2010

PubMed Abstract: TBX5, a member of the T-box transcription factor family, plays an important role in heart and limb development. More than 60 single point or deletion mutations of human TBX5 are associated with Holt-Oram syndrome that manifests itself as heart and limb malformations in 1 out of 100,000 live births. The majority of these mutations are located in the TBX5 T-box domain. We solved the crystal structures of the human TBX5 T-box domain in its DNA-unbound form and in complex with a natural DNA target site allowing for the first time the comparison between unbound and DNA-bound forms. Our analysis identifies a 3(10)-helix at the C-terminus of the T-box domain as an inducible recognition element, critically required for the interaction with DNA, as it only forms upon DNA binding and is unstructured in the DNA-unbound form. Using circular dichroism, we characterized the thermal stability of six TBX5 mutants containing single point mutations in the T-box domain (M74V, G80R, W121G, G169R, T223M, and R237W) and compared them with wild-type protein. Mutants G80R and W121G show drastically reduced thermal stability, while the other mutants only show a marginal stability decrease. For all TBX5 mutants, binding affinities to specific and nonspecific DNA sequences were determined using isothermal titration calorimetry. All TBX5 mutants show reduced binding affinities to a specific DNA target site, although to various degrees. Interestingly, all tested TBX5 mutants differ in their ability to bind unspecific DNA, indicating that both sequence-specific and unspecific binding might contribute to the misregulation of target gene expression.

PubMed: 20450920
DOI: 10.1016/J.JMB.2010.04.052

Experimental method

X-RAY DIFFRACTION (1.9 Å)