Structural basis of the bacteriophage TP901-1 CI repressor dimerization and interaction with DNA.
Rasmussen, K.K., Varming, A.K., Schmidt, S.N., Frandsen, K.E.H., Thulstrup, P.W., Jensen, M.R., Lo Leggio, L.(2018) FEBS Lett 592: 1738-1750
- PubMed: 29683476 
- DOI: https://doi.org/10.1002/1873-3468.13060
- Primary Citation of Related Structures:  
6FXA - PubMed Abstract: 
Temperate bacteriophages are known for their bistability, which in TP901-1 is controlled by two proteins, CI and MOR. Clear 1 repressor (CI) is hexameric and binds three palindromic operator sites via an N-terminal helix-turn-helix domain (NTD). A dimeric form, such as the truncated CI∆58 investigated here, is necessary for high-affinity binding to DNA. The crystal structure of the dimerization region (CTD 1 ) is determined here, showing that it forms a pair of helical hooks. This newly determined structure is used together with the known crystal structure of the CI-NTD and small angle X-ray scattering data, to determine the solution structure of CI∆58 in complex with a palindromic operator site, showing that the two NTDs bind on opposing sides of the DNA helix.
Organizational Affiliation: 
Department of Chemistry, University of Copenhagen, Denmark.