Anabaena xisF gene encodes a developmentally regulated site-specific recombinase.

Abstract

Two DNA elements are excised from the chromosome during Anabaena heterocyst differentiation. We have identified the gene xisF which encodes the site-specific recombinase responsible for the excision of a 55-kb element from within the fdxN gene. The cloned xisF gene is sufficient to cause site-specific rearrangement of an artificial substrate in Escherichia coil Inactivation of xisF in the Anabaena chromosome prevents excision of the fdxN element and growth in nitrogen-deficient medium but does not alter the development of heterocysts. Forced transcription of xisF in vegetative cells did not result in excision of the fdxN element, suggesting that other factors may be involved in cell-type specificity. The predicted XisF protein shows significant similarity to the Bacillus subtilis SpoIVCA recombinase.

Mpi recombinase globally modulates the surface architecture of a human commensal bacterium

“…The sizes and protein sequences of Ssr2 and Ssr3 identified them as members of the resolvase͞invertase branch of the Ssr family. In contrast, Ssr1 is larger (585 aa) and segregates into the large serine recombinase branch, whose members mediate integration (23), excision (24), and transposition (25) events, but not DNA inversion. Therefore, of these three Ssr products, only Ssr2 and Ssr3 were further considered as candidate DNA invertases.…”

Tansley Review No. 107. Heterocyst and akinete differentiation in cyanobacteria

“…Indeed, the nifHDK genes are contiguous in some heterocystous cyanobacteria, including some Nostoc strains and Fischerella ATCC 27929, as they are in all non-heterocystous strains (Tandeau de Marsac & Houmard, 1993). Inactivation of the xisF gene prevents N # fixation, but has no effect on heterocyst differentiation and pattern (Carrasco et al, 1994). Indeed, both the 11-kb (Oxelfelt et al, 1998 ;Bo$ hme, 1998) and the 55-kb (Haselkorn, 1992 ;Thiel et al, 1999) elements are absent from the genomes of a number of Anabaena and Nostoc strains.…”

“…These rearrangements involve the excision of an 11-kb element from nifD (Golden et al, 1988), a 55-kb element from fdxN (Golden et al, 1988), and a 10.5-kb element from hupL (Matveyev et al, 1994 ;Carrasco et al, 1995). These excisions are brought about by three excisases encoded by genes carried on the respective elements : xisA on the 11-kb element (Lammers et al, 1986) ; xisF on the 55-kb element (Carrasco et al, 1994) ; and xisC on the 10.5-kb element (Carrasco et al, 1995). They create the three functional operons nifHDK, nifB-fdxN-nifS-nifU, and hupSL, and leave the three elements as circular DNA molecules with no known function.…”

Cell‐type specificity of the Anabaena fdxN‐element rearrangement requires xisH and xisl

“…The element interrupts the fdxN open reading frame in the nifB-fdxN-nifS-nifU operon (Mulligan and Haselkorn, 1989). This rearrangement requires the xisF gene; inactivation of xisF blocks the fdxN-element rearrangement (Carrasco et a/., 1994). Failure to excise the element results in a strain that forms heterocysts (Hetf) but is unable to grow in the absence of fixed nitrogen, presumably because of the inability to produce functional nitrogenase (Nif-) as a result of polar effects on the expression of nifS and nifU.…”

“…It is not known if fdxN is essential for nitrogen fixation. The N-terminal third of XisF shows sequence similarity to members of the resolvase family of recombinases, and shows end-to-end similarity to SpolVCA and ORF469 (Stark et a/., 1992;Carrasco et a/., 1994;Matsuura et a/., 1995). SpolVCA is the recombinase necessary for excision of the 48 kb skin element during sporulation in B. subti/is (Kunkel et a/., 1990;Sat0 et a/., 1990).…”