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Title
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Modular organization of T4 DNA polymerase. Evidence from phylogenetics.
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Authors
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C.C.Wang,
L.S.Yeh,
J.D.Karam.
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Ref.
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J Biol Chem, 1995,
270,
26558-26564.
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PubMed id
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Abstract
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We describe the use of a phylogenetic approach to analyze the modular
organization of the single-chained (898 amino acids) and multifunctional DNA
polymerase of phage T4. We have identified, cloned in expression vectors, and
sequenced the DNA polymerase gene (gene 43) of phage RB69, a distant relative of
T4. The deduced primary structure of the RB69 protein (RB69 gp43) differs from
that of T4 gp43 in discrete clusters of short sequence that are interspersed
with clusters of high similarity between the two proteins. Despite these
differences, the two enzymes can substitute for each other in phage DNA
replication, although T4 gp43 does exhibit preference to its own genome. A
55-amino acid internal gp43 segment of high sequence divergence between T4 and
RB69 could be replaced in RB69 gp43 with the corresponding segment from T4
without loss of replication function. The reciprocal chimera and a deletion
mutant of the T4 gp43 segment were both inactive for replication and
specifically inhibitory ("dominant lethal") to the T4 wild-type allele. The
results show that phylogenetic markers can be used to construct chimeric and
truncated froms of gp43 that, although inactive for replication, can still
exhibit biological specificity.
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