Cloning and nucleotide sequence of the ColIb shufflon

The R64 shufflon is a novel type of DNA rearrangement in which four DNA segments invert independently or in groups. The related plasmid ColIb carries a variant shufflon. The present sequence analysis shows that the ColIb shufflon consists of three DNA segments that are highly homologous to the A, B, and C segments of the R64 shufflon. The 329-bp D segment of R64 is not present in the ColIb shufflon. As in the case of R64, the ColIb shufflon may act as a biological switch to select one of the six open reading frames in which the N-terminal region is constant while the C-terminal region is variable.