title: Acetylglutamate kinase-acetylglutamyl-phosphate reductase complex of Neurospora crassa. Evidence for two polypeptides.
abstract: Mutations at the arg-6 locus in Neurospora crassa are divided into two complementation groups (A and B) and a third noncomplementing group. There are many suppressible nonsense mutations among mutants in complementation group B and one in the noncomplementing group; no nonsense mutations exist among mutants in complementation group A (Davis, R. H., and Weiss, R. L. (1983) Mol. Gen. Genet. 192, 46-50). We show here that the mutants are defective in either or both of two enzymes of arginine biosynthesis, acetylglutamate kinase and/or acetylglutamyl-phosphate reductase. Mutants in complementation group A lack acetylglutamate kinase, those in complementation group B lack acetylglutamyl-phosphate reductase, and those in the noncomplementing group lack both activities. Mutants in group B also have reduced levels of acetylglutamate kinase. The enzymes from purified mitochondria are readily separable by gel filtration and by Blue A dye affinity chromatography. Acetylglutamate kinase appears to be an octamer with a molecular weight of 400,000, whereas acetylglutamyl-phosphate reductase appears to be a dimer with a molecular weight of 93,000. This suggests that the two activities reside on distinct polypeptides. These results are best accommodated by the following model: the arg-6 locus encodes a single mRNA which is translated into a single polypeptide; the latter is then cleaved post-translationally to yield two physically separable enzymes.
authors.forename: A U
authors.initials: AU
authors.lastname: Wandinger-Ness
authors.forename: E C
authors.initials: EC
authors.lastname: Wolf
authors.forename: R L
authors.initials: RL
authors.lastname: Weiss
authors.forename: R H
authors.initials: RH
authors.lastname: Davis
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics* / Q000302:isolation & purification; D005800:Genes, Fungal; D008957:Models, Genetic; D008970:Molecular Weight; D009154:Mutation; D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000201:enzymology* / Q000235:genetics; D010770:Phosphotransferases / Q000235:genetics* / Q000302:isolation & purification; D017851:Phosphotransferases (Carboxyl Group Acceptor); D012331:RNA, Fungal / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D012331:RNA, Fungal; D012333:RNA, Messenger; D000445:Aldehyde Oxidoreductases; C018722:N-acetyl-gamma-glutamyl-phosphate reductase; D010770:Phosphotransferases; D017851:Phosphotransferases (Carboxyl Group Acceptor); C018721:acetylglutamate kinase