BIOSYNTHESIS OF LIPOOLIGOSACCHARIDE NODULATION FACTORS - RHIZOBIUM-NODA PROTEIN IS INVOLVED IN N-ACYLATION OF THE CHITOOLIGOSACCHARIDE BACKBONE

Rhizobium meliloti interacts symbiotically with alfalfa by forming roo t nodules in which the bacteria fix nitrogen. The Rhizobium nodulation genes nodABC are involved in the synthesis of lipooligosaccharide sym biotic signal molecules, which are mono-N-acylated chitooligosaccharid es. These bacterial signals elicit nodule organogenesis in roots of le gumes. To elucidate the role of the NodA protein in lipooligosaccharid e biosynthesis, we prepared a radiolabeled tetrasaccharide precursor c arrying an amino group as a potential attachment site for N-acylation at the nonreducing glucosamine residue. Various criteria demonstrate t hat NodA is involved in the attachment of a fatty acyl chain to this t etrasaccharide precursor, yielding a biologically active nodulation fa ctor.