Final answer:
RuvAB proteins facilitate branch migration of Holliday junctions, during homologous recombination, essential for DNA repair and genetic diversity.
Step-by-step explanation:
RuvAB proteins are responsible for the branch migration of Holliday junctions during the process of homologous recombination. This is a critical step in DNA repair and recombination where RuvAB complexes help to move the crossover point of the junction along the DNA, which can increase genetic diversity or fix DNA damages.
Regarding the supplementary information provided about bacterial transcription, the σ (sigma) subunit of the RNA polymerase is involved in the initiation phase of transcription, as it helps in recognizing the promoter regions on the DNA sequence and initiates the process. In contrast, replication of the prokaryotic chromosome, touching on the concept of origin of replication, is unrelated to the function of RuvAB or the σ subunit in transcription.