Glycosylation Is Required for Outer Membrane Localization of the

The fucose-/mannose-specific lectin LecB from Pseudomonas aeruginosa is transported to the outer mem-brane; however, the mechanism used is not known so far. Here, we report that LecB is present in the periplasm of P. aeruginosa in two variants of different sizes. Both were functional and could be purified by their affinity to mannose. The difference in size was shown by a specific enzyme assay to be a result of N glycosylation, and inactivation of the glycosylation sites was shown by site-directed mutagenesis. Furthermore, we demonstrate that this glycosylation is required for the transport of LecB. Lectins are proteins of nonimmune origin that recognize and bind to specific carbohydrate structural epitopes without mod-ifying them. This group of carbohydrate proteins function as central mediators of information transfer in biological systems and perform their duties by interacting with glycoproteins, glycolipids, and oligosaccharides (34). Lectins exist in a wide range of organisms, including viruses, bacteria, plants, and animals, and are believed to play a general and important role in cell-cell interactions (9). Many bacteria have an arsenal o