Structure of a Synaptic 
Resolvase Tetramer Covalently Linked to Two Cleaved DNAs
Weikai Li,1
Satwik Kamtekar,1
Yong Xiong,1,2
Gary J. Sarkis,1*
Nigel D. F. Grindley,1
Thomas A. Steitz1,2,3
The structure of a synaptic intermediate of the site-specific recombinase 
resolvase covalently linked through Ser10 to two cleaved duplex DNAs has been determined at 3.4 angstrom resolution. This resolvase, activated for recombination by mutations, forms a tetramer whose structure is substantially changed from that of a presynaptic complex between dimeric resolvase and the cleavage site DNA. Because the two cleaved DNA duplexes that are to be recombined lie on opposite sides of the core tetramer, large movements of both protein and DNA are required to achieve strand exchange. The two dimers linked to the DNAs that are to be recombined are held together by a flat interface. This may allow a 180° rotation of one dimer relative to the other in order to reposition the DNA duplexes for strand exchange.
1 Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
2 Department of Chemistry, Yale University, New Haven, CT 06520, USA.
3 Howard Hughes Medical Institute, New Haven, CT 06520, USA.
* Present address: 454 Life Sciences, 20 Commercial Street, Branford, CT 06405, USA.
To whom correspondence should be addressed. E-mail: eatherton{at}csb.yale.edu