Nucleic Acids Research, Vol 26, Issue 15 3521-3527, Copyright © 1998 by Oxford University Press
SY Namgoong, S Sankaralingam and RM Harshey
We describe the isolation of a variant of Mu transposase (MuA protein)
which can recognize altered att sites at the ends of Mu DNA. No prior
knowledge of the structure of the DNA binding domain or its mode of
interaction with att DNA was necessary to obtain this variant. Protein
secondary structure programs initially helped target mutations to predicted
helical regions within a subdomain of MuA demonstrated to harbor att DNA
binding activity. Of the 54 mutant positions examined, only two showed
decreased affinity for att DNA, while eight others affected assembly of the
Mu transpososome. A variant impaired in DNA binding [MuA(R146V)], and
predicted to be in the recognition helix of an HTH motif, was challenged
with altered att sites created from degenerate oligonucleotides to select
for novel DNA binding specificity. DNA sequences bound to MuA(R146V) were
detected by gel- retardation, and following several steps of PCR
amplification/enrichment, were identified by cloning and sequencing. The
strategy allowed recovery of an altered att site for which MuA(R146V)
showed higher affinity than for the wild-type site, although this site was
bound by wild-type MuA as well. The altered association between MuA(R146V)
and an altered att site target was competent in transposition. We discuss
the strengths and limitations of this methodology, which has applications
in dissecting the functional role of specific protein-DNA associations.
ARTICLES
Altering the DNA-binding specificity of Mu transposase in vitro
Department of Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
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