Binding of the N-Terminal Domain of the Lactococcal Bacteriophage TP901-1 CI Repressor to Its Target DNA: A Crystallography, Small Angle Scattering, and Nuclear Magnetic Resonance Study

作者：Frandsen Kristian H; Rasmussen Kim K; Jensen Malene Ringkjobing; Hammer Karin; Pedersen Margit; Poulsen Jens Christian N; Arleth Lise; Lo Leggio Leila^*

来源：Biochemistry, 2013, 52(39): 6892-6904.

DOI：10.1021/bi400439y

In most temperate bacteriophages, regulation of the choice of lysogenic or lytic life cycle is controlled by a CI repressor protein. Inhibition of transcription is dependent on a helix-turn-helix motif, often located in the N-terminal domain (NTD), which binds to specific DNA sequences (operator sites). Here the crystal structure of the NTD of the CI repressor from phage TP901-1 has been determined at 1.6 angstrom resolution, and at 2.6 angstrom resolution in complex with a 9 bp double-stranded DNA fragment that constitutes a half-site of the O-L operator. This N-terminal construct, comprising residues 2-74 of the CI repressor, is monomeric in solution as shown by nuclear magnetic resonance (NMR), small angle X-ray scattering, and gel filtration and is monomeric in the crystal structures. The binding interface between the NTD and the half-site in the crystal is very similar to the interface that can be mapped by NMR in solution with a full palindromic site. The interactions seen in the complexes (in the crystal and in solution) explain the observed affinity for the O-R site that is lower than that for the O-L site and the specificity for the recognized DNA sequence in comparison to that for other repressors. Compared with many well-studied phage repressor systems, the NTD from TP901-1 CI has a longer extended scaffolding helix that, interestingly, is strongly conserved in putative repressors of Gram-positive pathogens. On the basis of sequence comparisons, we suggest that these bacteria also possess repressor/antirepressor systems similar to that found in phage TP901-1.

• 出版日期2013-10-1
• 单位中国地震局