Iron transport genes of the pJM1-mediated iron uptake system of Vibrio anguillarum are included in a transposonlike structure.

The pJM1 genes encoding the proteins involved in iron transport in the anguibactin iron uptake system were found to be flanked by insertion sequences in a composite transposonlike structure. These Vibrio anguillarum insertion sequences, ISV-A1 and ISV-A2, are related to IS903, IS102, and the ISVs found in Vibrio parahaemoliticus, Vibrio mimicus, and non-O1 Vibrio cholerae flanking various tdh (thermostable direct hemolysin) genes. The inverted repeats at the ends of ISV-A1 and ISV-A2 have no more than three mismatches when compared to the inverted repeats of the other ISVs or IS903 and IS102. ISV-A1 and ISV-A2 are flanked by 9-bp direct repeats, which is the number of bases that are duplicated upon IS903 or IS102 transposition. The similarities found between the V. anguillarum ISVs and the other ISVs as well as IS903 and IS102 suggest that they derive from a common ancestral insertion sequence. At the end of ISV-A1 there is a -35 sequence region followed by a -10 sequence found in the pJM1 sequence immediately outside the ISV. This promoter region is followed by an open reading frame with the potential to encode a polypeptide of 26,985 Da whose function is still unknown. The functionality of this promoter has been demonstrated and expression analysis showed that the promoter is regulated by the iron concentration of the media.