UNIQUE STRUCTURE OF THE DNA-BINDING DOMAIN OF INTERFERON REGULATORY FACTOR-2 DETERMINED BY NMR-SPECTROSCOPY

The secondary structure elements and the folding topology of the DNA-b inding domain of mouse interferon regulatory factor 2 [IRF-2(113)] wer e determined by heteronuclear multidimensional NMR spectroscopy. The s equential NOE (nuclear Overhauser effect) connectivities indicated the presence of three alpha-helical regions and four short beta-strands c onnected by relatively long loops. The long range NOEs indicated the f our strands form an antiparallel beta-sheet and the three alpha-helice s form a bundle on the sheet. The arrangement of the secondary structu re elements and the overall folding topology resemble those of the DNA binding domains of bacterial activator CAP, heat shock transcription factors and fork-head family transcription factors, although there is no sequence homology among them.