1 research outputs found
Complexity in efflux pump control: cross-regulation by the paralogues TtgV and TtgT
Pseudomonas putida DOT-T1E, known for its high
tolerance to solvents, possesses three Resistance–
Nodulation–Cell Division-type (RND) efflux pumps,
namely TtgABC, TtgDEF and TtgGHI, which are
involved in the active extrusion of solvents. Expression
of the ttgABC and ttgGHI operons was previously
shown to be regulated by the adjacently
encoded repressors, TtgR and TtgV, respectively.
Upstream of the third RND operon, ttgDEF, is located
a putative regulator gene, ttgT. In this study, TtgT is
shown to bind to the promoter region of the ttgDEF
operon, and to be released from DNA in the presence
of organic solvents. In vitro studies revealed that TtgV
and TtgT bind the same operator sites in both the
ttgDEF and the ttgGHI promoters. However, the affinity
of TtgV for the ttgDEF operator was higher than
that of TtgT, which, together with the fact that the ttgV
promoter seems to be almost twice stronger than the
ttgT promoter, explains why TtgV takes over in the
regulation of the two efflux pump operons. The functional
replacement of the cognate, chromosomally
encoded TtgT by the plasmid-encoded paralogue
TtgV illustrates a new mode of efflux pump regulation
of which the physiological relevance is discussed.This work was supported by Grant QLK3-CT2002-01923
from the European Commission and Grant BIO2006-05668
from the Spanish Comisión Interministerial de Ciencia y TecnologÃa
to J.L.R. and Grant RGY0021/2002 from the Human
Frontier Science Programme to M.-T.G. W.T. was the recipient
of a fellowship from the regional government of Andalusia,
Spain (Junta de AndalucÃa).Peer reviewe