Identification of a gene encoding a thioredoxin-like product necessary for cytochrome c biosynthesis and symbiotic nitrogen fixation in Rhizobium leguminosarum

• Published in: Journal of Bacteriology 1994-07, Vol.176 (13), p.4117-4123
• Main Authors: Vargas, C, Wu, G, Davies, A E, Downie, J A
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Bacteria; Bacteriology; Base Sequence; Biological and medical sciences; Carbon Monoxide - metabolism; citochromo c; cytochrome c; Cytochrome c Group - biosynthesis; Cytochrome c Group - chemistry; Cytochrome c Group - genetics; Economic plant physiology; Electron Transport Complex IV - analysis; fijacion del nitrogeno; fixation de l' azote; Flowers & plants; formation de nodosites; Fundamental and applied biological sciences. Psychology; gene; genes; Genes, Bacterial - genetics; Genetics; Light; Microbiology; Molecular Sequence Data; Mutation; nitrogen fixation; Nitrogen Fixation - genetics; nodulacion; nucleotide sequence; Oxygen Consumption - genetics; protein synthesis; proteinas; proteine; proteine soufree; proteins; Rhizobium leguminosarum; Rhizobium leguminosarum - genetics; root nodulation; secuencia nucleica; Sequence Homology, Amino Acid; sequence nucleique; sintesis de proteinas; Spectrophotometry; sulfoproteinas; sulphur proteins; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); synthese proteique; Thioredoxins - genetics; vicia hirsuta
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/jb.176.13.4117-4123.1994

A Tn5-induced mutant of Rhizobium leguminosarum bv. viciae could not form nitrogen-fixing nodules on pea or vetch because of a lesion in electron transport to oxygen. The mutant lacked spectroscopically detectable cytochromes c and aa3. No proteins containing c-type cytochromes could be identified in the mutant by heme staining of proteins fractionated on polyacrylamide gels, indicating that the mutant was defective in maturation of all c-type cytochromes. The Tn5 mutation was determined to be located in a gene that was called cycY. The cycY gene product is homologous to the thioredoxin-like protein HelX involved in the assembly of c-type cytochromes in Rhodobacter capsulatus and to an open reading frame from a Bradyrhizobium japonicum gene cluster containing other genes involved in cytochrome c biogenesis. Our observations are consistent with CycY functioning as a thioredoxin that reduces cysteine residues in apocytochromes c before heme attachment.