N. Perez et al., A functional assay in Escherichia coli to detect non-assisted interaction between galactose repressor dimers, NUCL ACID R, 28(18), 2000, pp. 3600-3604
Among the Escherichia coli operons repressed from multiple sites on DNA, th
e galactose operon is unique: its repression requires an auxiliary protein,
HU, to assist cooperative repressor binding to two distant DNA sites. Here
we show that GalR can still mediate repression from distant sites in an ar
tificial and simplified regulatory region which totally disturbs the organi
sation of the natural interactions. This simple and unexpected cooperation
of a protein incapable Of self-association in solution might be involved in
regulation of the gal operon. Furthermore, the assay may be generalised to
detection of rather weak cooperative interactions between DNA-bound protei
ns.