Isolation and sequence analysis of repA from the incurable 90 MDA plasmid of Azospirillum brasilense

An open reading frame encoding a protein of 312 amino acids was identified in an essential region of the 90 MDa plasmid of Azospirillum brasilense. The putative protein shows similarity with RepA proteins of plasmids of Sphingomonas aromacitovorans, Rhodotermus marinus, Chlorobium limicola and Bifidobacterium asteroides and with the RepA protein of the broad host range plasmid pSa. A putative helix-turn-helix motif was identified in the central part of the A. brasilense RepA protein. Analysis of the upstream and downstream region of the A. brasilense repA gene revealed the presence of eight 15-bp repeats, which can possibly function as iterons.