Other than the three annotated b-galactosidase genes, a novel b-galactosidase gene (galD) has been identified from Xanthomonas campestris pv. campestris. In this study, a 405-aa protein, ORF405, has been showed to markedly affect significant the b-galactosidase activity of GalD. Insertional inactivation of the orf405 gene decreased, although not completely abolished, the b-galactosidase activity of galD, while co-overexpression of galD and orf405 caused an apparent elevation on the b-galactosidase activity of GalD. This phenotype implied that ORF405 may be a b-galactosidase-stabilizing protein.
