A Mycoplasma genetic element resembling prokaryotic insertion sequences.

Nucleotide sequence analysis of two Mycoplasma hyopneumoniae-derived copies of a repetitive genetic element revealed structural similarities to typical prokaryotic insertion sequences. This is the first such sequence identified in the class Mollicutes. The element spans approximately 1550bp, with 28bp inverted terminal repeats. Two open reading frames occur within the sequence, one potentially encoding a protein with a size-variant alpha-helical domain containing heptameric leucine periodicity. Hybridization data with several strains from each of two mycoplasma species showed that the repetitive sequence is variably distributed within the M. hyopneumoniae and Mycoplasma hyorhinis chromosomes and indicated that in some cases the repeated sequence is contained within a larger genetic element which may be the result of phage or plasmid insertion.