Transcriptional Regulation of the Outer Membrane Protein A in

is known for its virulence in severely ill, hospitalized patients and for exhibiting multidrug resistance. infection treatment poses a serious problem in clinical environments. The outer membrane protein A () of the Acinetobacter genus is involved in bacterial virulence. Regulatory factors of in the post-transcriptional stage have been previously identified. However, the regulatory factors that act before the transcriptional stage remain unclear. We investigated the gene that encodes a putative transcription factor for expression in . A1S_0316 was purified and examined using size-exclusion chromatography, which revealed that it forms an oligomer. The binding affinity of A1S_0316 to the promoter region was also examined. We compared the binding affinity to the promotor region between A1S_0316 and the AbH-NS protein. A1S_0316 showed higher binding affinity to the promotor region than did H-NS. We examined the regulatory effect of these proteins on expression in using real-time qPCR and various in vitro tools. Our results indicated that A1S_0316 acts as an anti-repressor on the promotor region of the gene by inhibiting the binding of the AbH-NS protein. This study was the first demonstration of the transcriptional regulation of expression.