1XWR

Crystal structure of the coliphage lambda transcription activator protein CII

Summary for 1XWR

• Entry DOI: 10.2210/pdb1xwr/pdb
• Descriptor: Regulatory protein CII, ISOPROPYL ALCOHOL (3 entities in total)
• Functional Keywords: all-alpha fold, dna binding protein
• Biological source: Bacteriophage lambda
• Total number of polymer chains: 4
• Total formula weight: 44471.91

Authors

Datta, A.B.,Panjikar, S.,Weiss, M.S.,Chakrabarti, P.,Parrack, P. (deposition date: 2004-11-02, release date: 2005-06-21, Last modification date: 2024-03-13)

Primary citation

Datta, A.B.,Panjikar, S.,Weiss, M.S.,Chakrabarti, P.,Parrack, P.
Structure of {lambda} CII: Implications for recognition of direct-repeat DNA by an unusual tetrameric organization
Proc.Natl.Acad.Sci.USA, 102:11242-11247, 2005

PubMed Abstract: The temperate coliphage lambda, after infecting its host bacterium Escherichia coli, can develop either along the lytic or the lysogenic pathway. Crucial to the lysis/lysogeny decision is the homotetrameric transcription-activator protein CII (4 x 11 kDa) of the phage that binds to a unique direct-repeat sequence T-T-G-C-N6-T-T-G-C at each of the three phage promoters it activates: p(E), p(I), and p(aQ). Several regions of CII have been identified for its various functions (DNA binding, oligomerization, and susceptibility to host protease), but the crystal structure of the protein long remained elusive. Here, we present the three-dimensional structure of CII at 2.6-angstroms resolution. The CII monomer is comprised of four alpha helices and a disordered C terminus. The first three helices (alpha1-alpha3) form a compact domain, whereas the fourth helix (alpha4) protrudes in different orientations in each subunit. A four-helix bundle, formed by alpha4 from each subunit, holds the tetramer. The quaternary structure can be described as a dimer of dimers, but the tetramer does not exhibit a closed symmetry. This unusual quaternary arrangement allows the placement of the helix-turn-helix motifs of two of the four CII subunits for interaction with successive major grooves of B-DNA, from one face of DNA. This structure provides a simple explanation for how a homotetrameric protein may recognize a direct-repeat DNA sequence rather than the inverted-repeat sequences of most prokaryotic activators.

PubMed: 16061804
DOI: 10.1073/pnas.0504535102

Experimental method

X-RAY DIFFRACTION (2.56 Å)