The dual-incision nature of the reaction of UV-irradiated DNA catalyzed by the 
UvrABC complex potentially leads to excision of a damaged fragment. However, 
neither fragment release under nondenaturing conditions nor the UvrBC proteins 
are turned over. The addition of the UvrD protein to the incised DNA-UvrBC 
complex results in excision of the incised damaged strand and in the turnover of 
the UvrC protein. In an effort to better understand the involvement of UvrD in 
the excision step, immunoprecipitation was used to detect interacting proteins 
with UvrD in the DNA repair. In this communication, it is shown that UvrA and 
UvrB are precipitated with UvrD in solution but the UvrAB complex is not. In the 
incision complex, UvrB could be precipitated and the preincubation of UvrD with 
UvrB revealed an inhibitory effect on the turnover of the incision complex. 
These data imply that UvrB in the incision complex seems to recruit UvrD to the 
3' incised site of the incised strand by protein-protein interaction and to 
allow initiation of unwinding by UvrD from the resulting nick in a 3' to 5' 
direction.