This interaction presumably causes a conformational change in the actively bound subunit, providing for the efficient release of dTDP from its dTTP binding site. In the process of dTDP release, the ssDNA is transferred to the neighboring subunit, which undergoes a similar process.
The interaction likely triggers a structural adjustment in the subunit that has bound actively, enabling the rapid liberation of dTDP from its dTTP binding site. As dTDP is released, the single-stranded DNA is transferred to the neighboring subunit, which then undergoes a similar transformation.