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.
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.
Shoemaker
N B
NB
Department of Microbiology, University of Illinois, Urbana 61801, USA.
Wang
G R
GR
Salyers
A A
AA
D000595:Amino Acid Sequence; D001439:Bacteroides / Q000235:genetics*; D001483:Base Sequence; D004254:DNA Nucleotidyltransferases / Q000235:genetics*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D004270:DNA, Circular / Q000235:genetics; D019426:Integrases; D008969:Molecular Sequence Data; D012356:RNA, Transfer, Leu / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004270:DNA, Circular; D012356:RNA, Transfer, Leu; D004254:DNA Nucleotidyltransferases; D019426:Integrases