NodB

NodB is a protein encoded by the nodB gene in nitrogen-fixing rhizobia, and it is part of the nodulation (nod) gene cluster that governs the production of nodulation signals. It is typically described as a chitin deacetylase, or N-deacetylase, involved in the biosynthesis of Nod factors—the lipo-chito-oligosaccharide signals that induce legume root nodule formation.

In the Nod factor biosynthetic pathway, NodC polymerizes N-acetylglucosamine (GlcNAc) units into a chitooligosaccharide chain. NodB then deacetylates the non-reducing end GlcNAc residue, producing a glucosamine (GlcN) unit at that end. This deacetylation step is essential because it generates a substrate for NodA, which transfers a fatty acid to the amino group, yielding the mature Nod factor that is recognized by specific legume receptors. The modification of the oligosaccharide by NodB thus links chain synthesis to the subsequent acylation that defines Nod factor activity.

NodB genes are commonly located with nodABC, and often control by nodD in response to plant-derived signals such as flavonoids. The activity and structure of NodB can influence Nod factor architecture and, consequently, host range and nodulation efficiency. Variation in NodB among rhizobial species contributes to compatibility with different legume hosts, affecting the specificity of the symbiotic interaction.