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J. Bacteriol., Jun 1996, 3594-3600, Vol 178, No. 12
NB Shoemaker, GR Wang and AA Salyers
NBU1 is a 10.3-kbp integrated Bacteroides element that can be induced to
excise from the chromosome and can be mobilized to a recipient by
trans-acting functions provided by certain Bacteroides conjugative
transposons. The NBU1 transfer intermediate is a covalently closed circle,
which is presumed to be the form that integrates into the recipient genome.
We report here that a 2.4-kbp segment of NBU1 was all that was required for
site-specific integration into the chromosome of Bacteroides
thetaiotaomicron 5482. This 2.4-kbp region included the joined ends of the
NBU1 circular form (attN1) and a single open reading frame, intN1, which
encoded the integrase. Previously, we had found that NBU1 integrates
preferentially into a single site in B. thetaiotaomicron 5482. We have now
shown that the NBU1 target site is located at the 3' end of a Leu-tRNA
gene. The NBU1 integrase gene, intN1, was sequenced. The predicted protein
had little overall amino acid sequence similarity to any proteins in the
databases but had limited carboxy-terminal similarity to the integrases of
lambdoid phages and to the integrases of the gram-positive conjugative
transposons Tn916 and Tn1545. We also report that the intN1 gene is
expressed constitutively.
Copyright © 1996, American Society for Microbiology
The Bacteroides mobilizable insertion element, NBU1, integrates into the 3' end of a Leu-tRNA gene and has an integrase that is a member of the lambda integrase family
Department of Microbiology, University of Illinois, Urbana 61801, USA.
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