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PutA Protein, a Membrane-Associated Flavin Dehydrogenase, Acts as a Redox- Dependent Transcriptional Regulator
Paula Ostrovsky de Spicer and Stanley Maloy
Proceedings of the National Academy of Sciences of the United States of America
Vol. 90, No. 9 (May 1, 1993), pp. 4295-4298
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2361939
Page Count: 4
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The proline utilization (put) operon of Salmonella typhimurium is transcriptionally repressed by PutA protein in the absence of proline. PutA protein also carries out the enzymatic steps in proline catabolism. These two roles require different cellular localizations of PutA. Catabolism of proline requires PutA to associate with the membrane because reoxidation of the FAD cofactor in PutA needs the presence of an electron acceptor. Repression of the put operon requires PutA to bind to the put control-region DNA in the cytoplasm. The presence of proline, the inducer, is necessary but not sufficient for PutA to discriminate between its roles as an enzyme or as a repressor. Two conditions that prevent PutA protein binding to the put control region are (i) when proline and an electron acceptor or the cytoplasmic membrane are present or (ii) when PutA is reduced by dithionite. These two conditions increase the relative hydrophobicity of PutA protein, favoring membrane association and therefore enzymatic activity.
Proceedings of the National Academy of Sciences of the United States of America © 1993 National Academy of Sciences