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A Repressor Protein, PhaR, Regulates Polyhydroxyalkanoate (PHA) Synthesis via Its Direct Interaction with PHA
- Source :
- Journal of Bacteriology. 184:3992-4002
- Publication Year :
- 2002
- Publisher :
- American Society for Microbiology, 2002.
-
Abstract
- Phasins (PhaP) are predominantly polyhydroxyalkanoate (PHA) granule-associated proteins that positively affect PHA synthesis. Recently, we reported that the phaR gene, which is located downstream of phaP in Paracoccus denitrificans , codes for a negative regulator involved in PhaP expression. In this study, DNase I footprinting revealed that PhaR specifically binds to two regions located upstream of phaP and phaR , suggesting that PhaR plays a role in the regulation of phaP expression as well as autoregulation. Many TGC-rich sequences were found in upstream elements recognized by PhaR. PhaR in the crude lysate of recombinant Escherichia coli was able to rebind specifically to poly[( R )-3-hydroxybutyrate] [P(3HB)] granules. Furthermore, artificial P(3HB) granules and 3HB oligomers caused the dissociation of PhaR from PhaR-DNA complexes, but native PHA granules, which were covered with PhaP or other nonspecific proteins, did not cause the dissociation. These results suggest that PhaR is able to sense both the onset of PHA synthesis and the enlargement of the granules through direct binding to PHA. However, free PhaR is probably unable to sense the mature PHA granules which are already covered sufficiently with PhaP and/or other proteins. An in vitro expression experiment revealed that phaP expression was repressed by the addition of PhaR and was derepressed by the addition of P(3HB). Based on these findings, we present here a possible model accounting for the PhaR-mediated mechanism of PHA synthesis. Widespread distribution of PhaR homologs in short-chain-length PHA-producing bacteria suggests a common and important role of PhaR-mediated regulation of PHA synthesis.
- Subjects :
- Binding Sites
Physiology and Metabolism
Polyesters
Hydroxybutyrates
Repressor
DNA
Biology
biology.organism_classification
Microbiology
Polyhydroxyalkanoates
In vitro
DNA-Binding Proteins
Repressor Proteins
Bacterial Proteins
Biochemistry
Sense (molecular biology)
Paracoccus denitrificans
Expression Experiment
Molecular Biology
Gene
Bacteria
Subjects
Details
- ISSN :
- 10985530 and 00219193
- Volume :
- 184
- Database :
- OpenAIRE
- Journal :
- Journal of Bacteriology
- Accession number :
- edsair.doi.dedup.....50c89477a29841f5d8c9fc1cd9ea1995