Rates of flagellar- and P1 infective-phase variation by three site-specific recombinase genes in every possible combination.

Abstract

Rates of flagellar-and P1 infective-phase variation, caused by reversible inversion of an H(=PD) and a C segment, respectively, were examined with strains having the three site-specific recombinase genes, hin+, pin+, and cin+, in every possible combination. The variation rates were compared in terms of gene functions on the assumptions that the three genes are similar in gene dosage and comparable with one another in the amount of gene products and that each rate reflects an activity of a single gene or genes combined. The three genes were arranged in the order of the variation rate they caused; cin+> hin+> pin+ for both directions of H inversion, cin+>> hin+> >pin for C(+) inversion, and cin+>> pin+> hin+ for C(-) inversion. For C inversion the rates in a cin+ strain were higher than those in hint and pint by two or three orders of magnitude. It was suggested that for H inversion two couples of the genes, hin+ and pint and pin+ and cin+, function together, but hin+ and cin+ interact against each other and that for C inversion hint and pint interact synergistically, but function against cin+. The variation of P1 cin+ reached equilibrium at a ratio of C (+) /C (-) = 6.1/3.9 in the four kinds of lysogenic strains, and the generations bringing about the equilibrium ranged from 16 to 36 depending on the host gene(s) that function against cin+

Site-specific recombinase genes in three Shigella subgroups and nucleotide sequences of a pinB gene and an invertible B segment from Shigella boydii

“…X-Gal plates contained 40 mg of 5-bromo-4-chloro-3-indolyl-3-D-galactosidase (Sigma) per liter. Anti-flagellum serum against an e,n,x antigen was as previously described (31 (51) were deleted stepwise in opposite directions by using exonuclease III and mung-bean nuclease (Takara), and a series of deletion plasmids was used for sequencing. Nucleotide and amino acid sequences were analyzed by using DNASIS sequence analysis software (Hitachi Software Engineering Co.).…”

“…Since the rate from C(-) to C(+) by the cin gene has been reported to be 3.4 x 10-2 (31), it was determined that S. boydii and S. dysenteriae can mediate C inversion with frequencies three orders and one order of magnitude lower than that of the cin gene, respectively. A similar experiment was performed with S. sonnei, since our earlier study had suggested that this strain can mediate C inversion (48).…”

“…The positions and orientations of recombinase genes are also different from one another with respect to the invertible segment, although the G-gin and P-pin systems are similar in organization (13). Despite these differences, nucleotide sequences of inv sites where recombination takes place share high homology among the systems (14), and the recombinase genes are substitutable among them (24,27,31,50). These findings together with the relationship of the resolution system in transposon Tn3 to the switching system (45) have led to the idea that these switching systems have evolved from some composite structures in which recombinase genes have a common origin and in which the genes of the associated set(s) have an origin distinct from one another (24,25,43).…”

The site-specific recombinase encoded by pinD in Shigella dysenteriae is due to the presence of a defective Mu prophage

“…Phenotypic change caused by P inversion is unknown. In contrast to the difference in biological function, these recombinases are functionally interchangeable with one another (Kamp & Kahmann, 1981; Kutsukake & Iino, 1980; Momota & Enomoto, 1986; van de Putte et al ., 1984).…”