A single domain of the replication termination protein of Bacillus subtilis is involved in arresting both DnaB helicase and RNA polymerase

The current models that have been proposed to explain the mechanism of repl ication termination are (i) passive arrest of a replication fork by the ter minus (Ter) DNA-terminator protein complex that impedes the replication for k and the replicative helicase in a polar fashion and (ii) an active barrie r model in which the Ter-terminator protein complex arrests a fork not only by DNA-protein interaction but also by mechanistically significant termina tor protein-helicase interaction. Despite the existence of some evidence su pporting in vitro interaction between the replication terminator protein (R TP) and DnaB helicase, there has been continuing debate in the literature q uestioning the validity of the protein-protein interaction model. The objec tive of the present work was two-fold: (i) to reexamine the question of RTP -DnaB interaction by additional techniques and different mutant forms of RT P, and (ii) to investigate if a common domain of RTP is involved in the arr est of both helicase and RNA polymerase, The results validate and confirm t he RTP-DnaB interaction in vitro and suggest a critical role for this inter action in replication fork arrest. The results also show that the Tyr(33) r esidue of RTP plays a critical role both in the arrest of helicase and RNA polymerase.