This gene codes for the enzyme phosphoglucomutase (Pgm), a cytoplasmatic protein of 544 amino acids that is 75% identical to ExoC of A. tumefaciens and Mesorhizobium loti. ExoC (Pgm) is required in A. tumefaciens for virulence and in M. loti for nodulation. This phenotype was complemented by B. abortus pgm gene expressed under its own promoter. In M. loti and
A. tumefaciens pgm is part of the glycogen (gig) operon. Surprisingly, all the gig genes, except for pgm which is highly conserved, are absent in B. abortus. Pgm null mutants are avirulent, losing the ability to persist in the spleen of mice beyond four weeks. However, the ability to infect and multiply inside HeLa cells is partially conserved.
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