| Summary: | 碩士 === 國立交通大學 === 生物科技研究所 === 85 === Fumarase , one of the tricarboxylic acid cycle enzymes,
catalyzes the interconversion of fumarate and L-malate. Three
biochemically distinct fumarase have been reported in E.coli.
While the fumA and fumB genes encode heat-labile , iron-
containing fumarases , the fumC gene product is a heat-stable
fumarase which does not reguire iron for its activity. Although
three fumarase genes are regulated by Fnr and ArcA proteins ,
there still has some induction or repression during anaerobic
cell growth in fnr and ArcA proteins , there still has some
induction or repression during anaerobic cell growth in fnr and
arcA double mutant. Hence Fnr and ArcA might not be the only
reguirement for the anaerobic regulators of fumarase genes. A
topological state of the bacterial chromosome is important for
transcription , replication and recombination. To determine how
the fumA , fumB and fumC genes are regulated in response to a
variety of DNA supercoiling , inhibitors of gyrase and
topoisomerase mutation were induced into cells and examined. The
results indicated that the effect of supercoiling on expression
of three fumarase genes were more conspicious when cells were
grown under aerobic conditions. The existance of Fnr and ArcA
would affect the effect of varied DNA supercoiling structures on
fumA and fumB genes expression , while topA10 mutant caused an
increasement of fumC-lacZ expression. Therefore , the change of
DNA supercoiling structure will affect the expression of three
fumarase genes , and this control is part of mediated by Fnr and
ArcA regulators.
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