Linked Life Data

9201946

Source:http://linkedlifedata.com/resource/pubmed/id/9201946

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
26
pubmed:dateCreated
1997-7-21
pubmed:abstractText
The RNA-binding and RNA-DNA helicase activities of the Escherichia coli transcription termination factor rho have been investigated using natural RNA molecules that are 255 and 391 nucleotide residues in length and that contain the trp t' rho-dependent termination sequence of E. coli. Helicase substrates were prepared from these RNA molecules by annealing one or more DNA oligomers to complementary sequences located at or near the 3'-ends of the RNA molecules to form defined RNA-DNA hybrid sequences ranging in length from 20 to 100 bp. By comparing the fraction of the RNA molecules bound to rho with the fraction of bound DNA oligomers removed from the RNA during one round of the helicase reaction, we have shown that rho translocates processively at 37 degrees C in buffer containing 50 mM KCl. Helicase reactions and ATPase measurements were performed in parallel in the presence of RNA molecules containing RNA-DNA hybrids of various lengths, and we show that both the rate of translocation of the rho hexamer along the RNA chain and the rate of ATP consumption are similar, whether or not DNA is hybridized to the RNA transcript. By combining measurements of translocation and ATPase rates, we estimate that rho consumes approximately 1-2 ATP molecules in translocating over 1 nucleotide residue of the RNA chain at 37 degrees C in 50 mM KCl. The ATPase activity of rho remains the same after one round of the helicase reaction, indicating that rho appears to hydrolyze ATP at the same rate, whether it is translocating along the RNA, separating RNA-DNA hybrids, or bound at the 3'-end of the RNA substrate. We also show that rho binds cooperatively ( approximately 2-4 rho hexamers per RNA chain) to the RNA substrates under our standard helicase reaction conditions. However, cooperative binding is not essential for helicase activity, since this binding stoichiometry can be reduced to approximately 1.5 rho hexamers per 255-nucleotide residue RNA chain by blocking approximately 100 nt of either end of the rho binding site of the helicase substrate with complementary DNA oligonucleotides, with no change in helicase properties. The implications of these results for models of rho helicase function and for the role of rho in termination are discussed.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
36
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7993-8004
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Kinetics of the RNA-DNA helicase activity of Escherichia coli transcription termination factor rho. 2. Processivity, ATP consumption, and RNA binding.
pubmed:affiliation
Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't