we conducted tirfm experiments on a home - built microscope using nanofabricated dna curtains , as previously described . for all initial experiments , and for all kymograms shown in the manuscript , we used yoyo1 to stain the dna . yoyo1 does not affect the translocation rate or processivity of recbcd , nor did it affect the binding distributions of rnap , ecori , or nucleosomes ( not shown ) . in the presence of yoyo1 the roadblocks showed the same general response to collisions with recbcd , with identical distributions of ejection , stalling , and pushing ( and pushing velocities ) seen yoyo1 . however , yoyo1 reduced the distance obstacles were pushed by 2030% compared to minus yoyo1 reactions . therefore all sliding distances and half - lives reported in the manuscript correspond to values measured in the absence of yoyo1 . sliding distances are only reported for roadblocks that did not encounter any other qd - tagged proteins as they were pushed along the dna . this ensures that each analyzed collision / dissociation event only involved a single qd - tagged protein . many reactions were observed in which multiple qd - tagged roadblocks were pushed into one another , but in these cases we could not determine the order in which each qd - protein was displaced from the dna , and therefore could not measure sliding distances . for categorizing the event type distributions we defined  sliding  as any qd - tagged roadblock that moved more than 0.53 m ( ~1,950 bp ) , and anything less than this
in physiological settings nucleic acid translocases must act on substrates occupied by other proteins , and an increasingly appreciated role of translocases is to catalyze protein displacement from rna and dna1,2,3,4 . 
 however , little is known regarding the inevitable collisions that must occur , and the fate of protein obstacles and the mechanisms by which they are evicted from dna remain unexplored . 
 here we sought to establish the mechanistic basis for protein displacement from dna using recbcd as a model system . using nanofabricated curtains of dna and multi - color single - molecule microscopy , we visualized collisions between a model translocase and different dna - bound proteins in real time . 
 we show that the dna translocase recbcd can disrupt core rna polymerase ( rnap ) , holoenzyme , stalled elongation complexes , and transcribing rnap in either head - to - head or head - to - tail orientations , as well as ecorie111q , lac repressor and even nucleosomes . 
 recbcd did not pause during collisions and often pushed proteins thousands of base - pairs before evicting them from dna . 
 we conclude that recbcd overwhelms obstacles through direct transduction of chemomechanical force with no need for specific protein - protein interactions , and that proteins can be removed from dna through active disruption mechanisms that act on a transition state intermediate as they are pushed from one nonspecific site to the next .