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Isolation of the DNA sequence coding indole-3-glycerol phosphate synthetase and phosphoribosylanthranilate isomerase of Schizophyllum commune.

A Schizophyllum gene library was made in plasmid pRK9. Plasmids from this library were tested for their ability to complement several auxotrophic mutations of Escherichia coli. The goal was to isolate a Schizophyllum auxotrophic gene that could be used to transform a corresponding Schizophyllum auxotrophic mutant to prototrophy. Complementation was observed only for E. coli trpC indole 3-glycerol phosphate synthetase (IGPS) and phosphoribosyl-anthranilate isomerase (PRAI) mutations. Plasmids with a Schizophyllum sequence coding for both IGPS and PRAI activities were recovered from E. coli transformants. Expression of the Schizophyllum gene (TRP1) in E. coli is probably dependent on the Serratia marcescens promoter of plasmid pRK9. The DNA sequence containing the Schizophyllum TRP1 gene was not obviously rearranged in cloning.

Aldose-Ketose Isomerases↗

Sequence analysis of the URA1 gene encoding orotidine-5'-monophosphate decarboxylase of Schizophyllum commune.

The URA1 gene (encoding orotidine-5'-monophosphate decarboxylase) of the basidiomycete fungus Schizophyllum commune was mapped to a 1.4-kb BglI-BamHI fragment of two independent phage lambda clones previously isolated from a Schizophyllum genomic library. The fragment was identified by its ability to complement Schizophyllum ura1 mutants via transformation. The complete nucleotide sequence of the fragment containing the URA1 gene was determined. Sequence analysis revealed that the coding region of the URA1 gene encompasses a polypeptide of 279 amino acids (aa) interrupted by two small introns. The deduced aa sequence corresponds to 30.3 kDa and is substantially similar to the sequences of analogous polypeptides from other organisms. No canonical 5'-TATA sequence nor 3'-AATAAA polyadenylation signal are evident in the flanking regions of the URA1 gene.

Amino Acid Sequence↗

The isolation of specific genes from the basidiomycete Schizophyllum commune.

We have developed a routine way to isolate genes directly from the basidiomycete fungus, Schizophyllum commune. Plasmid DNA from a genomic gene library was used to isolate five specific genes by complementation of Schizophyllum mutations via transformation. The mutant strains were deficient in the ability to synthesize either adenine (ade2 and ade5), uracil (ura1, encoding orotidine-5'-phosphate decarboxylase; OMPdecase), tryptophan (trp1, encoding indole-3-glycerol phosphate synthetase; IGPS) or para aminobenzoic acid (pab1). In each case, Southern analysis revealed that transformation to prototrophy was concomitant with the integration of vector sequence into the genome of the S. commune mutant. Total DNA from transformants was restricted, religated, and used to transform E. coli. Ampicillin resistant plasmids were recovered from E. coli and tested for their ability to transform the corresponding mutant of S. commune. Plasmids complementing the ade2, ade5, pab1, trp1, and ura1 mutations were recovered.

Basidiomycota↗

Transformation of the basidiomycete, Schizophyllum commune.

Protoplasts of a Schizophyllum commune tryptophan auxotroph (trp1), deficient in indole-3-glycerol phosphate synthetase (IGPS), were transformed to trp+ with plasmid DNA containing the Schizophyllum TRP1 sequence. Efficiencies up to 30 transformants per microgram of plasmid DNA were obtained. Southern blots reveal that the transforming DNA is integrated in chromosomal DNA. The trp+ phenotype of transformants is stable in meiosis and mitosis. Transformants possess IGPS activity comparable to wild-type cells.

Basidiomycota↗

Cyanide-insensitive respiration in Schizophyllum commune.

Two mutants of the hymenomycete Schizophyllum commune, unable to use acetate as the sole carbon source for growth, were isolated. Growth of the mutants on a glucose minimal medium was only slightly inhibited by sodium azide. Genetic analysis revealed mutations in different chromosomal genes in the respective mutants. Both these mutants exhibited a high cyanide-insensitive endogenous respiration. The inhibition of the respiration by 8-hydroxyquinoline showed the mutants to respire predominantly by an alternative respiratory pathway observed in many fungal species, but not in the hymenomycetes so far. An enhanced cyanide-insensitive respiration was also found in a wild-type strain of Schizophyllum commune grown in the presence of sodium azide.

Acetates↗

Sequence organization of the nuclear DNA of Schizophyllum commune.

Several methods were used to characterize the organization of repetitive DNA in the fungus Schizophyllum commune. They all failed to show interspersion of repetitive sequences among single copy sequences. Saturation hybridization showed that 2.2% of the double-stranded nuclear DNA coded for rRNA. The size of the ribosomal cistron (11.9.10(6) daltons) was determined by restriction enzyme analysis. From these values it was calculated that about 6% of the nuclear DNA consisted of ribosomal cistrons, which approx. equals the amount of repetitive DNA present. Thus, this simple sequence organization in Schizophyllum commune is fundamentally different from organization patterns in higher eukaryotes.

Agaricales↗

Purification and characterization of an N-acetyl-D-galactosamine-specific lectin from the edible mushroom Schizophyllum commune.

An N-acetyl-D-galactosamine (GalNAc)-specific lectin was purified from the edible mushroom, Schizophyllum commune, using affinity chromatography on a porcine stomach mucin (PSM)-Sepharose 4B column. Under reducing and non-reducing conditions, SDS-polyacrylamide gel electrophoresis gave a major band of 31.5 kDa. The Schizophyllum commune lectin (SCL) showed high affinity toward rat erythrocytes and the sugar inhibition assay exhibited its sugar specificity highly toward lactose and N-acetyl-D-galactosamine. It was stable at 55 degrees C for 30 min and at pH 3-10 for 18-h test. The lectin was shown to be a glycoprotein with cytotoxic activity against human epidermoid carcinoma cells. The N-terminus of SCL was blocked but amino acid sequences of internal tryptic peptides showed moderately sequence similarities with some other fungal and plant lectins. Crystals of SCL were obtained by the sitting drop vapour-diffusion method using polyethylene glycol 8000 as the precipitant, and gave an X-ray diffraction pattern to approximately 3.8 angstroms resolution.

Acetylgalactosamine↗

The specificity determinant of the Y mating-type proteins of Schizophyllum commune is also essential for Y-Z protein binding.

This paper concerns the manner in which combinatorial mating proteins of the fungus, Schizophyllum commune, recognize one another to form complexes that regulate target gene expression. In Schizophyllum, tightly linked Y and Z mating-type genes do not promote development in the combinations present in haploid strains (i.e., self combinations). When the Y and Z genes from two different mating types are brought together by the fusion of two haploid cells, the Y and Z proteins from different mating types recognize one another as nonself, form a complex and activate development. Several Y and Z alleles are present in the population and all nonself combinations of Y and Z alleles are equally functional. We have made chimeric genes among Y1, Y3, Y4 and Y5 and examined their mating-type specificities by transformation and mating tests. These studies show that the specificity of Y protein recognized by Z protein is encoded within a short region of N-terminal amino acids. The critical region is not precisely the same in each Y protein and in each Y-Z protein interaction. For Y3 protein compared with Y4 protein, the critical residues are in an N-terminal region of 56 amino acids (residues 17-72), with 40% identity and 65% similarity. Two-hybrid studies show that: the first 144 amino acids of Y4 protein are sufficient to bind Z3 and Z5 proteins, but not Z4 protein, and proteins deleted of the Y4 specificity region do not bind Z3, Z4 or Z5 protein. Thus the specificity determinant of the Y protein is essential for protein-protein recognition, Y-Z protein binding and mating activity.

Alleles↗

ROLE OF CARBON DIOXIDE IN THE CONTROL OF FRUITING OF SCHIZOPHYLLUM COMMUNE.

Niederpruem, Donald J. (Indiana University Medical Center, Indianapolis). Role of carbon dioxide in the control of fruiting of Schizophyllum commune. J. Bacteriol. 85:1300-1308. 1963.-Compatible matings of Schizophyllum commune carried out in sealed chambers showed good vegetative growth and clamp-connection formation but fruiting was markedly inhibited. This inhibition was reversed by either aeration or the inclusion of alkali in the chambers. These phenomena occurred on a defined medium, with glucose as the primary carbon source, and were dependent on the level of carbohydrate employed. Gas mixtures of air-CO(2) (95:5) severely restricted the fruiting process when applied during mating or before the formation of fruit body primordia. It is proposed that respiratory CO(2) plays an important role in the regulation of form of S. commune.

Basidiomycota↗

RESPIRATION OF BASIDIOSPORES OF SCHIZOPHYLLUM COMMUNE.

Niederpruem, Donald J. (Indiana University Medical Center, Indianapolis). Respiration of basidiospores of Schizophyllum commune. J. Bacteriol. 88:210-215. 1964.-The aerobic metabolism of basidiospores of the wood-rotting mushroom Schizophyllum commune was investigated by use of manometric techniques and specific respiratory poisons. Basal respiration was stimulated markedly by the uncoupling agent 2,4-dinitrophenol. This effect was pH-dependent and was sensitive to antimycin A. A positive periodic acid-Schiff reaction and a respiratory quotient (CO(2)/O(2)) of near unity pointed to carbohydrate as the endogenous substrate. Oxygen consumption was increased by sucrose, certain hexoses, d-xylose, acetate, and ethanol. Oxidative assimilation was evident with d-glucose and acetate. Glucose oxidation was inhibited by cyanide, azide, antimycin A, Atabrine, and phenylmercuric acetate. These data implicate cytochrome oxidase, b- and c-type cytochromes, flavoprotein, and essential sulfhydryl groups in basidiospore respiration.

2,4-Dinitrophenol↗

FINE STRUCTURE OF BASIDIOSPORES OF SCHIZOPHYLLUM COMMUNE.

Voelz, Herbert (University of West Virginia, Morgantown), and Donald J. Niederpruem. Fine structure of basidiospores of Schizophyllum commune. J. Bacteriol. 88:1497-1502. 1964.-The fine structure of basidiospores of the wood-rotting mushroom Schizophyllum commune was elucidated. Ungerminated spores were characterized by a fibrous cell wall, a cytoplasmic membrane, electron-dense granules, nuclei surrounded by nuclear envelopes with pores, and poorly defined mitochondria. Young germlings were still binucleate, whereas mitochondria appeared highly organized. Vacuolization appeared with germination, and elaborate pore structures were associated with septa.

Basidiomycota↗

POLYOL METABOLISM IN THE BASIDIOMYCETE SCHIZOPHYLLUM COMMUNE.

Niederpruem, Donald J. (Indiana University Medical Center, Indianapolis), Amtul Hafiz, and Lyle Henry. Polyol metabolism in the basidiomycete Schizophyllum commune. J. Bacteriol. 89:954-959. 1965.-The polyol metabolism of intact cells and extracts of the wood-rotting mushroom Schizophyllum commune was investigated during the developmental cycle. Exogenous polyols stimulated the cellular respiration of germlings, but were without effect on that of ungerminated basidiospores. Requisite enzymes of polyol metabolism were demonstrated in extracts of spores and of subsequent stages of development. Oxidation of mannitol and sorbitol appeared to be coupled to nicotinamide adenine dinucleotide (NAD) reduction and was favored in alkaline medium. Ketohexose formation was shown during mannitol oxidation, and the NAD-dependent oxidation of xylitol yielded ketopentose. Xylitol oxidation with nicotinamide adenine dinucleotide phosphate (NADP) as hydrogen acceptor led to pentose formation. Oxidation of reduced NAD was enhanced by fructose but not by sorbose. Reduction of aldohexose and pentose was dependent upon reduced NADP, and pentose reductase was maximal at pH 6.8. The specific activity of mannitol dehydrogenase was highest in extracts of vegetative mycelium. Growth in either glucose or xylose media had no significant effect on enzymes of polyol metabolism.

Alcohols↗

Purification and some properties of cholesterol oxidase from Schizophyllum commune with covalently bound flavin.

Cholesterol oxidase [EC 1.1.3.6] from Schizophyllum commune was purified by an affinity chromatography using 3-O-succinylcholesterol-ethylenediamine (3-cholesteryl-3-[2-aminoethylamido]propionate) Sepharose gels. The resulting preparation was homogeneous as judged by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 53,000 by SDS-gel electrophoresis and 46,000 by sedimentation equilibrium. The enzyme contained 483 amino acid residues as calculated on the basis of the molecular weight of 53,000. The enzyme consumed 60 mumol of O2/min per mg of protein with 1.3 mM cholesterol at 37 degrees C. The enzyme showed the highest activity with cholesterol; 3 beta-hydroxysteroids, such as dehydroepiandrosterone, pregnenolone, and lanosterol, were also oxidized at slower rates. Ergosterol was not oxidized by the enzyme. The Km for cholesterol was 0.33 mM and the optimal pH was 5.0. The enzyme is a flavoprotein which shows a visible absorption spectrum having peaks at 353 nm and 455 nm in 0.1 M acetate buffer, pH 4.0. The spectrum was characterized by the hypsochromic shift of the second absorption peak of the bound flavin. The bound flavin was reduced on anaerobic addition of a model substrate, dehydroepiandrosterone. Neither acid not heat treatment released the flavin coenzyme from the enzyme protein. The flavin of the enzyme could be easily released from the enzyme protein in acid-soluble form as flavin peptides when the enzyme protein was digested with trypsin plus chymotrypsin. The mobilities of the aminoacyl flavin after hydrolysis of the flavin peptides on thin layer chromatography and high voltage electrophoresis differed from those of free FAD, FMN, and riboflavin. A pKa value of 5.1 was obtained from pH-dependent fluorescence quenching process of the aminoacyl flavin. AMP was detected by hydrolysis of the flavin peptides with nucleotide pyrophosphatase. The results indicate strongly that cholesterol oxidase from Schizophyllum commune contains FAD as the prothetic group, which is covalently linked to the enzyme protein. The properties of the bound FAD were comparable to those of N (1)-histidyl FAD.

3-Hydroxysteroid Dehydrogenases↗

The mating-type locus B alpha 1 of Schizophyllum commune contains a pheromone receptor gene and putative pheromone genes.

Analysis of the multispecific B alpha mating-type locus of Schizophyllum commune provided evidence that pheromones and pheromone receptors govern recognition of self versus non-self and sexual development in this homobasidiomycetous fungus. Four subclones of an 8.2 kb genomic fragment carrying B alpha 1 specificity induced B-regulated sexual morphogenesis when introduced into a strain with one of the eight compatible B alpha specificities that are known to exist in nature. One of these clones, which activated all other B alpha specificities, contains a gene termed bar1. The predicted protein product of bar1, as well as that of bar2, a homologous gene isolated from a B alpha 2 strain, has significant homology to known fungal pheromone receptor proteins in the rhodopsin-like superfamily of G protein-linked receptors. The other three active B alpha 1 clones were subcloned further to identify the minimal active element in each clone. Every active subclone contains a putative pheromone gene ending in a signal for possible isoprenylation. A message of approximately 600 bp was observed for one of these genes, bap1(1). This paper presents the first evidence for a system of multiple pheromones and pheromone receptors as a basis for multispecific mating types in a fungus.

Amino Acid Sequence↗

Flavin substrate specificity of the vitamin B2-aldehyde-forming enzyme from Schizophyllum commune.

Vitamin B2-aldehyde-forming enzyme from Schizophyllum commune catalyzes oxidation of the 5'-hydroxymethyl of riboflavin to the formyl group. We have monitored enzyme activity by spectrophotometrically measuring the reduction of 2,6-dichlorophenol-indolphenol as electron acceptor to assess 35 riboflavin analogs as potential substrates or competitive inhibitors with the purpose of delimiting structural requirements of the substrate binding site. Analogs with side chains of two- to six-carbon length modified by deletion of secondary hydroxyls or by changes in their epimeric configuration are not oxidized. The omega-hydroxyalkyl-flavins (n = 2-6) are competitive inhibitors (Ki = 7-16 microM) of riboflavin oxidation, as are some analogs with L-secondary hydroxyls in the side chain. Analogs with bulky substituents on the isoalloxazine ring are also not substrates. The enzyme does not significantly bind flavins with an 8 alpha-N-imidazole; diethylamino, methylethylamino, dimethylamino, ethylamino, or ethoxy groups at position 8; methyl at 6; and beta-hydroxyethylamino at position 2. Also the replacement of N with CH in 1-deazariboflavin disallows substrate reaction. Analogs with fluoro, chloro, methyl, amino, or methylamino at position 8; chloro at 7; methyl or carboxylmethyl at 3; thio at 2, and C replacing N at positions 3 or 5 are substrates with relative Vmax values ranging from 27 to 110% that of riboflavin. The Km values for the analogs oxidized are all found to be in the micromolar range (22-176 microM). Overall specificity of the enzyme for riboflavin is found to be rather narrow and sterically limited, which suggests that the vitamin is the natural substrate.

Alcohol Oxidoreductases↗

Cellobiose dehydrogenase from Schizophyllum commune: purification and study of some catalytic, inactivation, and cellulose-binding properties.

Cellobiose dehydrogenase (CDH) of Schizophyllum commune was purified to homogeneity. It is a glycoprotein with a molecular mass of 102, 000. Cellulosic substrates can serve as substrates for CDH. Cytochrome c, dichlorophenol-indophenol, ferricyanide, and oxygen can be reduced by the enzyme. CDH is stable in the pH range of 4-11 and up to 35 degrees C. The enzyme keeps active at high concentrations of H2O2. In the presence of cellobiose and Fe3+, incubation of CDH resulted in its inactivation and the degree of the inactivation was dependent mainly on the amount of CDH and cellobiose present. CDH has a distinct and specific affinity to cellulose and showed the strongest binding to acid-treated cellulose. The adsorption isotherm data fitted the Langmuir-type equation. The uv-visible spectra of the oxidized and reduced states of CDH showed a typical cytochrome b-type pattern. Addition of dithionite eliminated the adsorption between 440 and 500 nm, which indicates the presence of a flavin group in CDH.

Carbohydrate Dehydrogenases↗

Interaction of the A alpha Y and Z mating-type homeodomain proteins of Schizophyllum commune detected by the two-hybrid system.

The A alpha locus is one of four mating-type loci that control sexual development in Schizophyllum commune. A alpha has nine alternative mating types (A alpha 1-A alpha 9) which encode specific alleles of two homeodomain-related proteins, Y and Z. For example, proteins Y4 and Z4 are encoded by A alpha 4, and Y5 and Z5 are encoded by A alpha 5. Our previous studies showed that A alpha-regulated development is activated in fusion cells between haploid strains by the presence of Y and Z proteins derived from different A alpha mating types (e.g., Y4 and Z5), but not by proteins from the same mating type (e.g., Y4 and Z4). In this study we analyzed protein-protein interactions of Y4 with the Z4 and Z5 isoforms in a two-hybrid system. Protein interactions were detected in filter and liquid assays for beta-galactosidase with Y4 and Z5, a non-self, developmentally active combination, but not with Y4 and Z4, a self, developmentally inactive combination. These results support the hypothesis that non-self combinations of Y and Z form a heteromultimer that activates development, but that self combinations do not. Although developmental target genes directly regulated by the A alpha locus have yet to be identified, it is assumed on the basis of motifs encoded that the Y-Z heteromultimer acts as a transcription factor.

Base Sequence↗

The A alpha mating-type transcripts of Schizophyllum commune.

A alpha 1, A alpha 3, and A alpha 4 ds- and ss-DNA probes from the polymorphic A alpha mating-type locus of Schizophyllum commune were used to probe Northern blots of poly(A+) RNA extracted from strains of various A alpha mating types. The purpose of these experiments was to identify, map, and characterize the transcripts produced from the regions of the A alpha locus. The transcripts unique to A alpha mating type map colinear with the open reading frames identified from DNA sequence and are encoded within the fragments which activate the A developmental pathway in transformation. These data confirm the existence and structure of the previously hypothesized Y and Z A alpha mating-type genes. Transcripts from the Y and Z genes are present in vegetative cells of homokaryons and dikaryons and in cells of the fruiting bodies. The presence of the transcripts throughout the life cycle is consistent with the model of Y and Z proteins as "master switches" of A-regulated development.

Blotting, Northern↗