1xwr
From Proteopedia
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Crystal structure of the coliphage lambda transcription activator protein CII
Overview
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.
About this Structure
1XWR is a Single protein structure of sequence from Enterobacteria phage lambda with IPA as ligand. Full crystallographic information is available from OCA.
Reference
Structure of lambda CII: implications for recognition of direct-repeat DNA by an unusual tetrameric organization., Datta AB, Panjikar S, Weiss MS, Chakrabarti P, Parrack P, Proc Natl Acad Sci U S A. 2005 Aug 9;102(32):11242-7. Epub 2005 Aug 1. PMID:16061804
Page seeded by OCA on Wed Nov 21 06:23:45 2007
