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J. Bacteriol., 07 1996, 4004-4011, Vol 178, No. 14
N Tojo, K Sanmiya, H Sugawara, S Inouye and T Komano
Mx8 is a generalized transducing phage that infects Myxococcus xanthus
cells. This phage is lysogenized in M. xanthus cells by the integration of
its DNA into the host chromosome through site-specific recombination. Here,
we characterize the mechanism of Mx8 integration into the M. xanthus
chromosome. The Mx8 attachment site, attP, the M. xanthus chromosome
attachment site, attB, and two phage-host junctions, attL and attR, were
cloned and sequenced. Sequence alignments of attP, attB, attL, and attR
sites revealed a 29-bp segment that is absolutely conserved in all four
sequences. The intP gene of Mx8 was found to encode a basic protein that
has 533 amino acids and that carries two domains conserved in site-specific
recombinases of the integrase family. Surprisingly, the attP site was
located within the coding sequence of the intP gene. Hence, the integration
of Mx8 into the M. xanthus chromosome results in the conversion of the intP
gene to a new gene designated intR. As a result of this conversion, the
112-residue C- terminal sequence of the intP protein is replaced with a
13-residue sequence. A 3-base deletion within the C-terminal region had no
effect on Mx8 integration into the chromosome, while a frameshift mutation
with the addition of 1 base at the same site blocked integration activity.
This result indicates that the C-terminal region is required for the
enzymatic function of the intP product.
Copyright © 1996, American Society for Microbiology
Integration of bacteriophage Mx8 into the Myxococcus xanthus chromosome causes a structural alteration at the C-terminal region of the IntP protein
Department of Biology, Tokyo Metropolitan University, Japan.
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