Fructose phosphotransferase system of Xanthomonas campestris pv. campestris: characterization of the fruB gene.

In the plant pathogen Xanthomonas campestris pv. campestris, fructose is transported by a specific phosphotransferase system (PTS). This PTS involves a multiphosphoryl transfer protein (MTP) encoded by the fruB gene, which was cloned and sequenced. fruB is part of a transcriptional unit together with the fruK gene, coding for 1-phosphofructokinase, which is located upstream from the fruA gene, coding for the fructose-specific permease (EIIB'BCFru). The amino acid sequence of the X. campestris MTP deduced from the fruB sequence shared 46% identical residues with an MTP identified in Rhodobacter capsulatus. The X. campestris MTP (837 amino acid residues) consists of three moieties: a fructose-specific enzyme-IIA-like N-terminal moiety (residues 1-148), followed by an HPr-like moiety (161-251) and an enzyme-I-like C-terminal moiety (274-837). The three domains are separated by two flexible hinge regions rich in proline and alanine residues. The construction of a fruB mutant confirmed the role of the MTP in fructose transport and phosphorylation in X. campestris.