OmpR, the transcriptional regulator of the ompF and ompC porin genes,
is a member of a novel class of DNA-binding proteins. The mechanism(s)
by which this class of proteins interacts with target DNA sites is no
t understood. To address this issue, we investigated the nature of the
DNA sequences recognized by OmpR. A 36 bp DNA fragment was identified
that is capable of supporting OmpR-DNA interaction in vivo. The base
pairs within this region of DNA that are critical to this interaction
were identified by isolating mutations within the fragment that hinder
normal OmpR-DNA binding. The results obtained provide insights concer
ning the nature of the sequences recognized by OmpR and also support a
model in which co-operative binding is involved in OmpR-DNA interacti
on.