INVESTIGADORES
DE PRAT GAY Gonzalo
congresos y reuniones científicas
Título:
The DNA binding helix of papillomavirus E2 protein: local versus context dependent conformation.
Autor/es:
WETZLER, D.E. AND PRAT GAY, G. DE
Lugar:
Angra dos Reis, R.J., Brasil, 8-12 de noviembre de 2004.
Reunión:
Congreso; First Latin American Protein Society Meeting; 2004
Institución organizadora:
The Protein Society
Resumen:
The DNA binding helix of papillomavirus E2 protein: local versus context depenedent conformation. Diana Wetzler and Gonzalo de Prat-Gay Instituto Leloir, Patricias Argentinas 435 (1405) Buenos Aires, Argentina. The DNA binding domain of papillomavirus E2 transcriptional regulator has a unique dimeric ß-barrel topology only shared with the EBNA1 origin binding protein from Epstein Barr virus. The DNA binding helix folds against a central ß-barrel constituted by 4 strands of each monomer and was shown to be higlhy dynamic but with persistent structure. A 19 residue peptide corresponding to this helix lacks regular secondary structure in solution with an increase in type II polyproline structure evidenced from the tempearture effect on the CD spectra. Trifluoroethanol (TFE) titration follows a two state transition and stabilizes a helical population of 10 residues, in agreement with the residues adopting helical conformation in the full domain, with a free energy change of 2 kcal/mol. No peptide concentration dependent secondary structure change was observed between 10 and 200 µM, neither in the absence or presence of TFE, indicating no oligomerization dependent structure. Addition of guanidine chloride evidences an ellipticity maximum at 218 nm, indicative of PII structure. However, circular dichroism and fluorescence anisotropy titrations as well as electrophoretic mobility shift show no DNA binding activity or, if any weak binding may occur, the affinity has to be 50,000-fold lower than the full domain. The inability of large excess of the E2 DNA site to induce helical conformation or to bind to the peptide indicates that the conformation of the major DNA binding helix in the full domain is not fully flexible and most likely it is not further stabilized or ordered upon DNA binding.
