How DNA repair proteins sort through a genome for damage is one of the 
fundamental unanswered questions in this field. To address this problem, we 
uniquely labeled bacterial UvrA and UvrB with differently colored quantum dots 
and visualized how they interacted with DNA individually or together using 
oblique-angle fluorescence microscopy. UvrA was observed to utilize a 
three-dimensional search mechanism, binding transiently to the DNA for short 
periods (7 s). UvrA also was observed jumping from one DNA molecule to another 
over approximately 1 microm distances. Two UvrBs can bind to a UvrA dimer and 
collapse the search dimensionality of UvrA from three to one dimension by 
inducing a substantial number of UvrAB complexes to slide along the DNA. Three 
types of sliding motion were characterized: random diffusion, paused motion, and 
directed motion. This UvrB-induced change in mode of searching permits more 
rapid and efficient scanning of the genome for damage.