Multiple mutant of Escherichia coli synthesizing virtually thymineless DNA during limited growth.
AUTOR(ES)
el-Hajj, H H
RESUMO
The dut gene of Escherichia coli encodes deoxyuridine triphosphatase, an enzyme that prevents the incorporation of dUTP into DNA and that is needed in the de novo biosynthesis of thymidylate. We produced a conditionally lethal dut(Ts) mutation and isolated a phenotypic revertant that had a mutation in an unknown gene tentatively designated dus (for dut suppressor). The dus mutation restored the ability of the dut mutant to grow at 42 degrees C without restoring its enzymatic activity or thymidylate independence. A strain was constructed bearing, in addition to these mutations, ones affecting the following genes and their corresponding products: ung, which produces uracil-DNA N-glycosylase, a repair enzyme that removes uracil from DNA; deoA, which produces thymidine (deoxyuridine) phosphorylase, which would degrade exogenous deoxyuridine; and thyA, which produces thymidylate synthase. When grown at 42 degrees C in minimal medium containing deoxyuridine, the multiple mutant displayed a 93 to 96% substitution of uracil for thymine in new DNA. Growth stopped after the cellular DNA had increased 1.6- to 1.9-fold and the cell mass had increased 1.7- to 2.7-fold, suggesting a general failure of macromolecular biosynthesis. DNA hybridization confirmed that the uracil-containing DNA was chromosomal and that new rounds of initiation must have occurred during its synthesis.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=206231Documentos Relacionados
- Transport-Limited Growth Rates in a Mutant of Escherichia coli
- Modulation of cell wall synthesis by DNA replication in Escherichia coli during initiation of cell growth.
- Thymineless death in Escherichia coli dnaB mutants and in a dnaB dnaG double mutant.
- SYNCHRONIZATION OF DIVISION OF A THYMINELESS MUTANT OF ESCHERICHIA COLI1
- Morphological analysis of the division cycle of two Escherichia coli substrains during slow growth.