A new family of plant transcription factors displays a novel ssDNA-binding surface.
The crystal structure of p24, the single-stranded DNA (ssDNA) binding subunit of the plant defense transcription factor PBF-2, has been determined to 2.3 A resolution. p24 is representative of a novel family of ubiquitous plant-specific proteins that we refer to as the Whirly family because of their quaternary structure. PBF-2 is composed of four p24 molecules that interact through a helix-loop-helix motif. This interaction produces a central pore, with beta-strands radiating outwards, resulting in a whirligig appearance to the quaternary structure. The noncrystallographic C(4) symmetry arrangement of p24 subunits is novel for ssDNA binding proteins and may explain the binding specificity of PBF-2. This structural arrangement also supports the role of PBF-2 in binding melted promoter regions to modulate gene expression.
Desveaux
Darrell
D
Department of Biochemistry, Université de Montréal, CP 6128, Station Centre-Ville, Montréal, Québec, H3C 3J7, Canada.
Allard
Julie
J
Brisson
Normand
N
Sygusch
Jurgen
J
D000595:Amino Acid Sequence; D001665:Binding Sites; D015153:Blotting, Western; D002850:Chromatography, Gel; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D018506:Gene Expression Regulation, Plant; D018257:Helix-Loop-Helix Motifs; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D010944:Plants / Q000737:chemistry*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*
D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C416516:PBF-2 protein, Solanum tuberosum; D010940:Plant Proteins; D014157:Transcription Factors