Ter sites are recognized by
Ter sites are specific DNA sequences within termination region where replication fork arrest occurs. Tus, terminus utilization substance, 36 kilodalton monomer, recognizes 23 base pair ter consensus through major groove contacts forming tight stoichiometric complex with Kd near one nanomolar. Upon approach of DnaB helicase from blocking direction, C-terminal region of Tus locks onto helicase halting advancement. DnaA and SeqA proteins bind origin not terminus sequence. Tus-ter pair thus functions as replication fork trap ensuring forks meet within termination zone avoiding over-replication.
Ref: NCBI Bookshelf, Lewin Genes: Tus protein recognizes ter sites forming polar fork trap, replication termination