I wish to thank all the coauthors of this study and our colleagues from Nowotny lab. We are also grateful to @iimcb.bsky.social, @ncn.gov.pl and Solaris National Synchrotron Radiation Centre for making this project possible!

Finally, we deliver the first complete cryo-EM structure of a two-component recombinase composed of ICP8 annealase and UL12 alkaline nuclease. The complex was reconstituted using a model DNA with a dsDNA and 3′ ssDNA overhang.

We are also presenting a cryo-EM reconstruction of a double filament of ICP8 at 3.2 Å resolution. We visualize the interactions between protein subunits within and between the antiparallel strands. DNA used to produce the filaments could not be traced.

A very similar DNA conformation is observed in the crystal structures of ICP8 with 14-mer ssDNA. ICP8 subunits form dimers with a two-fold symmetry, with their DNA-binding sites facing each other and the outward-rotated bases of bound DNAs form pairs in a flexible manner.

We determined a cryo-EM structure of BALF2 bound to ssDNA at 3.2 Å resolution. The visible fragment of DNA is accommodated in a positively charged cleft. In the first four nucleotides, the base edges face the protein, but the next three bases are rotated away from the protein.