The Transactivation Region of the FIS Protein that Controls Site-Specific DNA Inversion Contains Extended Mobile  Beta-Hairpin Arms   

Safo, M. K., Yang, W. Z., Corselli, L., Cramton, S. E., Yuan, H. S., Johnson, R. C.   

       Fis is an Escherichia coli site-specific DNA-binding protein that functions as a regulator of many different reactions. X-ray crystal structure analyses have been carried out for wild-type Fis. The C-terminal of Fis comprises a helix-turn-helix DNA binding motif (C and D helices), however, the N-terminus of Fis, sequence 1 to 25, that is required to promote in-mediated DNA inversion, is not resolved in the crystal structure. A new crystal form of a mutant Fis protein Glu36-Lys now reveals that the trans-activation region contains two beta-hairpin arms that protrude over 20 Angstrom from the protein core. The newly resolved beta-hairpin arm at the Fis N-terminal region could be responsible for interacting with invertases.
 
The EMBO Journal 16:6860-6873, 1997