Linked Life Data

21515672

Source:http://linkedlifedata.com/resource/pubmed/id/21515672

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
23
pubmed:dateCreated
2011-6-6
pubmed:abstractText
The helicase and primase activities of the hexameric ring-shaped T7 gp4 protein reside in two separate domains connected by a linker region. This linker region is part of the subunit interface between monomers, and point mutations in this region have deleterious effects on the helicase functions. One such linker region mutant, A257T, is analogous to the A359T mutant of the homologous human mitochondrial DNA helicase Twinkle, which is linked to diseases such as progressive external opthalmoplegia. Electron microscopy studies show that A257T gp4 is normal in forming rings with dTTP, but the rings do not assemble efficiently on the DNA. Therefore, A257T, unlike the WT gp4, does not preassemble on the unwinding DNA substrate with dTTP without Mg(II), and its DNA unwinding activity in ensemble assays is slow and limited by the DNA loading rate. Single molecule assays measured a 45 times slower rate of A257T loading on DNA compared with WT gp4. Interestingly, once loaded, A257T has almost WT-like translocation and DNA unwinding activities. Strikingly, A257T preassembles stably on the DNA in the presence of T7 DNA polymerase, which restores the ensemble unwinding activity of A257T to ?75% of WT, and the rescue does not require DNA synthesis. The DNA loading rate of A257T, however, remains slow even in the presence of the polymerase, which explains why A257T does not support T7 phage growth. Similar types of defects in the related human mitochondrial DNA helicase may be responsible for inefficient DNA replication leading to the disease states.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
1083-351X
pubmed:author
pubmed:issnType
Electronic
pubmed:day
10
pubmed:volume
286
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
20490-9
pubmed:meshHeading
pubmed:year
2011
pubmed:articleTitle
A257T linker region mutant of T7 helicase-primase protein is defective in DNA loading and rescued by T7 DNA polymerase.
pubmed:affiliation
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, N.I.H., Extramural