Characterization of HscC (Hsc62), homologue of Hsp70 in Escherichia coli: over-expression of HscC modulates the activity of house keeping sigma factor σ70
✍ Scribed by Mohammad Arifuzzaman; Taku Oshima; Shinsuke Nakade; Hirotada Mori
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 251 KB
- Volume
- 7
- Category
- Article
- ISSN
- 1356-9597
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✦ Synopsis
Abstract
Background: HscC, the third member of the Hsp70 family in Escherichia coli, shares 33% identity with the other two homologues, DnaK and HscA, and displays ATPase activity. Genetic and biochemical evidence indicates that the DnaK‐DnaJ chaperone system interacts with σ^32^ and is involved in the negative regulation of the heat shock response. Although HscC is a highly conserved protein in the Hsp70 family, its function is still unknown.
Results: We observed that the over‐expression of HscC caused severe growth inhibition. To explore this effect, we performed primer extension analysis and a β‐galactosidase assay and found that HscC reduced the σ^70^‐dependent promoter activity. An i__n vitro__ transcription assay revealed that HscC inhibited σ^70^‐dependent transcription. In addition, the co‐purification analysis showed that σ^70^ co‐eluted with HscC.
Conclusion: These results indicate that HscC forms a complex with σ^70^ and may function as its negative modulator.