2Z43: Structure Of A Twinned Crystal Of Rada

RecA family proteins engage in an ATP-dependent DNA strand exchange reaction that includes a ssDNA nucleoprotein helical filament and a homologous dsDNA sequence. In spite of more than 20 years of efforts, the molecular mechanism of homology pairing and strand exchange is still not fully understood. Here we report a crystal structure of Sulfolobus solfataricus RadA overwound right-handed filament with three monomers per helical pitch. This structure reveals conformational details of the first ssDNA binding disordered loop (denoted L1 motif) and the dsDNA binding N-terminal domain (NTD). L1 and NTD together form an outwardly open palm structure on the outer surface of the helical filament. Inside this palm structure, five conserved basic amino acid residues (K27, K60, R117, R223 and R229) surround a 25 A pocket that is wide enough to accommodate anionic ssDNA, dsDNA or both. Biochemical analyses demonstrate that these five positively charged residues are essential for DNA binding and for RadA-catalyzed D-loop formation. We suggest that the overwound right-handed RadA filament represents a functional conformation in the homology search and pairing reaction. A new structural model is proposed for the homologous interactions between a RadA-ssDNA nucleoprotein filament and its dsDNA target.
PDB ID: 2Z43Download
MMDB ID: 60704
PDB Deposition Date: 2007/6/12
Updated in MMDB: 2007/11
Experimental Method:
x-ray diffraction
Resolution: 1.93  Å
Source Organism:
Similar Structures:
Biological Unit for 2Z43: monomeric; determined by author
Molecular Components in 2Z43
Label Count Molecule
Protein (1 molecule)
DNA Repair and Recombination Protein Rada(Gene symbol: SSO_RS01235)
Molecule annotation
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Citing MMDB