Gin mutants that can be suppressed by a Fis-independent mutation.
The Gin invertase of bacteriophage Mu mediates recombination between two inverted gix sites. Recombination requires the presence of a second protein, Fis, which binds to an enhancer sequence. We have isolated 24 different mutants of Gin that are impaired in DNA inversion but proficient in DNA binding. Six of these mutants could be suppressed for inversion by introduction of a second mutation, which when present in the wild-type gin gene causes a Fis-independent phenotype. Only one of the six resulting double mutants shows an inversion efficiency which is comparable to that of the wild-type Gin and which is independent of Fis. The corresponding mutation, M to I at position 108 (M108I), is located in a putative alpha-helical structure, which in the homologous gamma delta resolvase has been implicated in dimerization. The properties of the M108I mutant suggest that in Gin this dimerization helix might also be the target for Fis interaction. The five other mutants that show a restored inversion after introduction of a Fis-independent mutation appear to be completely dependent on Fis for this inversion. The corresponding mutations are located in different domains of the protein. The properties of these mutants in connection with the role of Fis in inversion will be discussed.
Spaeny-Dekking
L
L
Laboratory of Molecular Genetics, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, The Netherlands.
Schlicher
E
E
Franken
K
K
van de Putte
P
P
Goosen
N
N
D010583:Bacteriophage mu / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D007446:Chromosome Inversion; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011995:Recombination, Genetic / Q000235:genetics*; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
D002352:Carrier Proteins; D004279:DNA, Viral; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; D014764:Viral Proteins; C054767:gin protein, Enterobacteria phage Mu; D004264:DNA Topoisomerases, Type I