We have altered the antibiotic resistance of the reporter plasmids and the pJG4-5 activation-domain and pEG202 DNA binding-domain plasmids used in the Brent interaction trap/two-hybrid system. These plasmids were each previously ampicillin-resistant, resulting in an inefficient purification of any one plasmid from a yeast strain containing all three plasmids that constitute the complete interaction trap. By creating derivatives of each of these plasmids expressing either kanamycin or chloramphenicol resistance, along with the parent plasmids, we now have the option to use the interaction trap in yeast with three E. coli differentially selectable vectors. This will allow isolation of any one plasmid by purifying all of the interaction trap plasmids from yeast simultaneously and plating E. coli transformed with the plasmids onto the appropriate antibiotic plate to select the particular plasmid of interest.