Structural and biophysical insights into the ligand-free Pitx2 homeodomain and a ring dermoid of the cornea inducing homeodomain mutant.
The homeodomain-containing transcription factor Pitx2 (pituitary homeobox protein 2) is present in many developing embryonic tissues, including the heart. Its homeodomain is responsible for the recognition and binding to target DNA sequences and thus constitutes a major functional unit in the Pitx2 protein. Nuclear magnetic resonance techniques were employed to determine the solution structure of the native Pitx2 homeodomain and a R24H mutant that causes autosomal dominantly inherited ring dermoid of the cornea syndrome. The structures reveal that both isoforms possess the canonical homeodomain fold. However, the R24H mutation results in a 2-fold increase in DNA binding affinity and a 5 °C decrease in thermal stability, while changing the dynamic environment of the homeodomain only locally. When introduced into full-length Pitx2c, the mutation results in an only 25% loss of transactivation activity. Our data correlate well with clinical observations suggesting a milder deficiency for the R24H mutation compared to those of other Pitx2 homeodomain mutations.
Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45267, United States.
Thomas
T
Doerdelmann
Douglas J
DJ
Kojetin
Jamie M
JM
Baird-Titus
Laura A
LA
Solt
Thomas P
TP
Burris
Mark
M
Rance
D000595:Amino Acid Sequence; D055592:Biophysical Phenomena; D003229:Conjunctival Diseases / Q000235:genetics*; D003316:Corneal Diseases / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D003884:Dermoid Cyst / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D006639:Histidine; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008156:Luciferases / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D012996:Solutions; D013816:Thermodynamics; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000097577:Homeobox Protein PITX2
D004247:DNA; D006639:Histidine; D018398:Homeodomain Proteins; D008024:Ligands; D008156:Luciferases; D012996:Solutions; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2