DNA Binding Proteins of the Filamentous Phages CTXφ and VGJφ of Vibrio cholerae

The native product of open reading frame 112(orf112) and a recombinant variant of the RstB protein, encoded by Vibrio cholerae pathogen-specific bacteriophages VGJ phi and CTX phi, respectively, were purified to more than 90% homogeneity. Orf112 protein was shown to specifically bind single-stranded genomic DNA of VGJ phi; however, RstB protein unexpectedly bound double-stranded DNA in addition to the single-stranded genomic DNA. The DNA binding properties of these proteins may explain their requirement for the rolling circle replication of the respective phages and RstB's requirement for single-stranded-DNA chromosomal integration of CTX phi phage dependent on XerCD recombinases.