Rica Dela Cruz Mentor: Dr. Monica Chander SoxR is a redox-
sensitive transcriptional dual regulator and activator protein.
Homologs of this protein, in addition to the specific DNA
sequences it binds, exist in various bacterial species.
Traditionally, SoxR has been known to be an oxidative stress-
defense protein, such as in the enteric bacterium, E. coli. In
the presence of oxidative stress agents, SoxR’s characteristic
iron-sulfur clusters become oxidized inducing a conformational
change. This allows the protein to bind to a specific DNA
promoter site to activate the expression of certain genes, which
in turn produce various antioxidant proteins. Unlike E. coli,
however, studies in other bacterial species have suggested that
SoxR may play a role in the transport and/or modification of
small molecules within the cell. For example, it has recently
been found that SoxR regulates the efflux of the redox-active
antibiotic, pyocynin, produced by the bacteria, Pseudomonas
aeruginosa. Analogous to P. aeruginosa, the