Spectroscopic studies on an oxygen-binding haemoglobin-like flavohaemoprotein from Escherichia coli.
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ABSTRACT:
SUBMITTER: Ioannidis N
PROVIDER: S-EPMC1132060 | biostudies-other | 1992 Dec
REPOSITORIES: biostudies-other
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Project description:We used trimethylpsoralen intercalation to map supercoiling across the E. coli chromosome. We treated E. coli cells with trimethylpsoralen and exposed them to UV light. Psoralen enters cells, intercalates between DNA base pairs, and crosslinks the two strands of DNA at a rate proportional to the local superhelical density. We then fragmented DNA and hybridized crosslinked and non-crosslinked DNA fragments separately to tiling microarrays.
2016-03-22 | GSE77687 | GEO
Project description:In Escherichia coli the RNA chaperone Hfq is involved in riboregulation by assisting base-pairing between small regulatory RNAs (sRNAs) and mRNA targets. Several structural and biochemical studies revealed RNA binding sites on either surface of the donut shaped Hfq-hexamer. Whereas sRNAs are believed to contact preferentially the YKH motifs present on the proximal site, poly(A)(15) and ADP were shown to bind to tripartite binding motifs (ARE) circularly positioned on the distal site. Hfq has been reported to bind and to hydrolyze ATP. Here, we present the crystal structure of a C-terminally truncated variant of E. coli Hfq (Hfq(65)) in complex with ATP, showing that it binds to the distal R-sites. In addition, we revisited the reported ATPase activity of full length Hfq purified to homogeneity. At variance with previous reports, no ATPase activity was observed for Hfq. In addition, FRET assays neither indicated an impact of ATP on annealing of two model oligoribonucleotides nor did the presence of ATP induce strand displacement. Moreover, ATP did not lead to destabilization of binary and ternary Hfq-RNA complexes, unless a vast stoichiometric excess of ATP was used. Taken together, these studies strongly suggest that ATP is dispensable for and does not interfere with Hfq-mediated RNA transactions.
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