Mutants Neurospora

N.r. of Neurospora crassa has M, 228,000. A N.r. mutant (Neurospora crassa nit-3) produces a subunit of N.r. containing cytochrome and Mo (M, 160,000) this does not react with NAD(P)H, but transfers electrons to nitrate from exogenous FADH2 or reduced methyl viologen. The other component is produced by Neurospora crassa nit-I it is unable to reduce nitrate, but catalyses the reduction of cytochrome c by NAD(P)H. 

The use of mutant 34486 of Neurospora crassa for the microbiological assay of ch oline has been described (8). A physiological method has also been used in which the ch oline is extracted after hydrolysis from a sample of biological material and acetylated. The acetylcholine is then assayed by a kymographic procedure, in which its effect in causing contraction of a piece of isolated rabbit intestine is measured (33). 

The molybdenum cofactor was liberated from D. gigas AOR, and under appropriate conditions was transferred quantitatively to nitrate reductase in extracts of Neurospora crassa nit-1 mutant) to yield active nitrate reductase 217). On the basis of molybdenum content, the activity observed for reconstitution with molybdenum cofactor of D. gigas was lower (25%) than the values observed for the procedure using extractable molybdenum cofactor of XO, used as reference. This result can now be put in the context of the difference in pterin present (MPT-XO and MCD-AOR) 218). 

Goldie, A.H. and Subden, R.E., The neutral carotenoids of wild-type and mutant strains of Neurospora crassa, Biochem. Genet. 10, 275, 1973. 

Purification and characterisation of galactose-induced pectinases from the exo-1 mutant strain of Neurospora crassa... 

However, Phinney (8) has suggested on the basis of experiments with mutants of Neurospora that the biosynthesis of cysteine involves the coupling of sulfate with an organic compound (presumably cysteine sulfinic acid) followed by reduction to sulfide. He noted also that sulfate may be reduced stepwise to sulfide and may then enter the protein as such. But he observed this process proceeds less readily than when sulfate combines first with protein. 

Beadle and Tatum had found that irradiation of Neurospora spores produced mutants which were incapable of carrying out certain well-defined chemical reactions, and it was at first supposed that as a result of the destruction of a specific gene, the potentiality for producing a particular enzyme was completely lost. The "wild type" of Neurospora could propagate satisfactorily when biotin was the only vitamin-like substance supplied in the culture medium. Of the many mutant strains produced, however, one needed, in addition to biotin, the vitamin riboflavin. Without a supply of riboflavin in the culture medium this so-called "riboflavinless mutant" would not grow. Since riboflavin is a part of an enzyme system always found in Neurospora, it is an obligatory cell constituent and either has to be produced by the cells themselves (as in the wild type) or supplied exogenously in... 

DIMS was identified as the responsible gene for one of DNA hypomethylation mutants in Neurospora crassa (Tamaru and Selker, 2001). This is the first report that histone (H3K9) methylation regulates DNA methylation. Furthermore, it is reported that this regulation is mediated through the HPl recruitment to the tri-methylated H3K9 loci (Freitag et al, 2004), but it remains to be elucidated whether DNA methylation (DNA methyltransferase) is directly controlled (recruited) by HPl. 

Gardner GF, Feldman JF 1981 Temperature compensation of circadian periodicity in clock mutants of Neurospora crassa. Plant Physiol 68 1244-1248 Gorl M, Merrow M, Huttner B, Johnson J, Roenneberg T, Brunner M 2001 A PEST-hke element in FREQUENCY determines the length of the circadian period in Neurospora crassa. EMBO J 20 7074-7084... 

Young Is part of the Neurospora genome project s goal an attempt to make mutants all along each of the chromosomes ... 

Enzyme Systems. Carotenoid biosynthesis by crude cell-free preparations from Halobacterium cutirubrum 0-carotene), Phycomyces blakesleeanus mutants (/8-carotene), and a Neurospora crassa mutant (phytoene) has been demonstrated. Detailed studies of carotenogenic enzymes from tomato fruit... 

Neurospora crassa (wild type and 286-lOHSa mutant [1]) [1] <4> Penicillium chrysogenum (Q-176 [1]) [1]... 

The isolation of 5-formyl-2-methylpyrimidine (62) and 5-amino-2-methylpyrimidine (63) from thiamin requiring mutants of Neurospora has led to a suggestion that these may be late intermediates in the biosynthesis of (45), a contention supported in part by the demonstration of conversion of the amino compound (63) to the hydroxymethylpyrimidine (45) by yeast cell-free extracts. 

The recognition that the Mo in the molybdoproteins exists in organic cofactor forms came from studies of mutants of Aspergillus and Neurospora.650 In 1964, Pateman and associates discovered mutants that lacked both nitrate reductase and xanthine dehydrogenase. Later, it was shown that acid-treated molybdoenzymes released a material that would restore activity to the inactived nitrate reductase from the mutant organisms. This new coenzyme, a phosphate ester of molybdopterin (Fig. 15-17), was characterized by Rajagopalan and coworkers.650 651 A more complex form of the coenzyme, molybdopterin cytosine dinucleotide... 

The shikimate pathway was identified through the study of ultraviolet light-induced mutants of E. coli, Aerobacter aerogenes, and Neurospora. In 1950, using the penicillin enrichment technique (Chapter 26), Davis obtained a series of mutants of E. coli that would not grow without the addition of aromatic substances.4 5 A number of the mutants required five compounds tyrosine, phenylalanine, tryptophan, p-aminobenzoic acid, and a trace of p-hydroxybenzoic acid. It was a surprise to find that the requirements for all five compounds could be met by the addition of shikimic acid, an aliphatic compound that was then regarded as a rare plant acid. Thus, shikimate was implicated as an intermediate in the biosynthesis of the three aromatic amino acids and of other essential aromatic substances.6 7... 

Early clues to the nature of the pyrimidine pathway were provided by the observations that orotic acid (6-carboxyuracil, fig. 23.12) can satisfy the growth requirement of mutants of the fungus Neurospora that are unable to make pyrimidines, and that isotopically labeled orotate is an immediate precursor of pyrimidines in Neurospora and a number of bacteria. 

Nason, A., Lee, K.Y., Pan, S.-S., Ketchum, P.A., Lamberti, A. Davies, J. (1971). In vitro formation of assimilatory reduced nicotinamide adenine dinucleotide phosphate nitrate reductase from a Neurospora mutant and a component of molybdenum-enzymes. Proceedings of the National Academy of Sciences (USA) 68, 3242-6. 

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