The nodulation gene nolK of Azorhizobium caulinodans is involved in the formation of GDP-fucose from GDP-mannose.
The nolK gene of Azorhizobium caulinodans is essential for the incorporation of a fucosyl group in Nod factors. A NAD(P)-binding site is present in the NolK amino acid sequence and the gene is homologous to Escherichia coli genes, presumably involved in GDP-fucose synthesis. Protein extracts of A. caulinodans, overexpressing nolK, have an enzyme activity that synthesizes GDP-fucose from GDP-mannose. nolK most probably encodes a 4-reductase performing the last step in GDP-fucose synthesis. Wild-type A. caulinodans produces a population of fucosylated and non-fucosylated molecules but the nolK-overexpressing strain produces only fucosylated Nod factors. Thus, the production of activated fucosyl donors is a rate-limiting step in Nod factor fucosylation.
Mergaert
P
P
Department of Genetics, Flanders Interuniversity Institute for Biotechnology (VIB), Universiteit Gent, Belgium.
Van Montagu
M
M
Holsters
M
M
D005643:Fucose / Q000378:metabolism; D005647:Fucosyltransferases / Q000378:metabolism; D005798:Genes, Bacterial; D006154:Guanosine Diphosphate Fucose / Q000096:biosynthesis* / Q000737:chemistry; D006155:Guanosine Diphosphate Mannose / Q000096:biosynthesis* / Q000737:chemistry; D009586:Nitrogen Fixation / Q000235:genetics / Q000502:physiology*; D012230:Rhizobiaceae / Q000235:genetics* / Q000502:physiology
D006154:Guanosine Diphosphate Fucose; D005643:Fucose; D006155:Guanosine Diphosphate Mannose; D005647:Fucosyltransferases