Architecture of the gamma delta resolvase synaptosome: oriented heterodimers identity interactions essential for synapsis and recombination.

Gammadelta resolvase catalyzes recombination within a complex nucleoprotein structure containing at least 12 resolvase subunits bound to two 114 bp res sites. The 2,3' interaction between resolvase dimers is essential for synapsis and recombination. Using oriented resolvase heterodimers, we have identified half sites of res that must be occupied by a 2,3'-proficient protomer. For synapsis, only four of the eight subunits bound to sites II and III, those at II-L and III-L, require a 2,3'-proficient interface. This 2,3' interaction, apparently between protomers bound to adjacent sites, may nucleate assembly of the core synaptic complex. For recombination, 2,3'-proficient subunits are also required at sites I-R and III-R, suggesting an important communication between the crossover site and the core of the synapse.