The Gin recombination system of bacteriophage Mu mediates
the inversion of the Gsegment of the phage genome. The phenotypic effect
of this inversion is the expression of alternate sets of tail-fiber genes.
The tangle model of Sumners et al [QRB 28, 3 (1995), pp. 253-313] is used
in our work to study Gin recombination. It is proved that, under certain
mathematical and biological assumptions, the model for the Gin action proposed
by R. Kanaar [Kanaar et. al, Cell 62, 353-366] is correct. Therefore Gin
is found to be specific for the (-2,0) synaptic complex. On the other hand,
Gin recombination requires three accessory factors: the protein Fis, an
enhancer sequence, and negatively supercoiled DNA substrate. In order to
understand the roles played by these factors in the enzymatic action, a
mutant of Gin that requires neither one of them was created and has been
studied [Crisona et. al, J Mol Biol 243,3 (1994), pp. 437-457)]. The tangle
model is used to develop software and prove that this mutant is not specific
for the (-2,0) synaptic complex and to enumerate reaction pathways for
all observed products. |
