Aminopeptidasen des Ascomyceten Podospora anserina

Zusammenfassung Aus dem Wildstamm des Ascomyceten Podospora anserina wurden zwei Aminopeptidasen isoliert, die immunologisch nicht verwandt sind: P1 hat ein MG von ung. 140000, sie kann durch Hitzebehandlung aktiviert werden (z. B. 8 min bei 80° C um 100%) und wird von DFP (5 mM) vollständig gehemmt. Wie Hydrolyseversuche mit über 30 Oligopeptiden zeigten, hat sie eine ziemlich enge Substratspezifität (z. B. für Ala-Pro, Gly-Pro-Ala, Glu-Gly-Phe und Valinpeptide). P1 wird durch Behandlung mit 0,1% SDS nicht in Untereinheiten gespalten.P2, eine typische (Leucin) aminopeptidase, hat ein MG von etwa 70000, sie wird durch Hitze nicht aktiviert und durch DFP kaum gehemmt. P2 ist sehr unspezifisch und hydrolysiert alle getesteten Oligopeptide, wie z. B. Di- und Triglycin, Pro-, Asp-, Glu- und Trp-Peptide, die oxydierten Insulin-A- und (z. T.)-B-Ketten, jedoch nicht das native Protein. P2 wird durch 0,1% SDS in inaktive Untereinheiten (MG um 15000) gespalten, die reaggregieren können, wobei aktive Proteine von etwa 35000 bzw. 150000 entstehen, jedoch keine P2 (70000) mehr. Daraus und aus Untersuchungen mit der Immundiskelektrophorese wird geschlossen, daß die (Leucin)aminopeptidase P2 von P. anserina aus Untereinheiten besteht, die abhängig von noch unbekannten Bedingungen mehr oder weniger aggregiert vorliegen können.Dies wird auch durch die Verhältnisse bei der rhythmischen Mutante zonata bestätigt: Hier konnte P1 nicht nachgewiesen werden, dagegen wurde ein Enzym (Pz) isoliert, das serologisch mit P2 verwandt ist, in verdünnter Lösung jedoch ein MG von 35000 aufwies. Pz bildet in der Diskelektrophorese eine sehr breite Bande, der K _m -Wert des Enzyms (um 10^-3) für Leu-4-NA liegt um das 10fache höher als beim Wildenzym.Morphologische und cytochemische Ähnlichkeiten zwischen zonata und solchem wild-Mycel, in dem eine heterogenische (vegetative) Inkompatibilitätsreaktion abläuft (z. B. anomaler Wuchs, freie AP-Aktivität im Cytoplasma), werden diskutiert.

---

Aminopeptidases from the ascomycete Podospora anserina Genetical differences between the wild strain and the mutant zonata

Summary Two immunologically unrelated aminopeptidases (P1 and P2) from the wild strain of the Ascomycete Podospora anserina were isolated and characterized. P1 has a molecular weight (MW) of about 140000, it can be activated by heat treatment (e. g. 8 min/80° C=100%) and is completely inhibited by DFP (5 mM). The enzyme specificity was tested with more than 30 oligopeptides as substrates, However, few of them were attacked significantly (Ala-Pro, Gly-Pro-Ala, Glu-Gly-Phe and two valine peptides). P1 is not cleaved into subunits by treatment with 0.1% SDS, but serological tests indicate the existence of a dimer in crude mycelial extracts.P2 (a typical leucine aminopeptidase) has a MW of about 70000. There is no heat activation and no inhibition by DFP. It has a large substrate range, hydrolyzing all oligopeptides tested, including di- and triglycine, pro-, asp-, glu-, and trp-peptides. Oxydized A- and B-chains of insuline are also partly digested but not the native protein. P2 is cleaved by 0.1% SDS into inactive subunits (MW about 15000) which may be reaggregated yielding active proteins with MWs of approximately 35000 and 150000 but no aggregates of the original MW of 70000.From these facts and from immunoelectrophoretical investigations it is concluded that the (leucine) aminopeptidase P2 is composed of subunits, which appear more or less aggregated, depending on conditions still unknown.This is corroborated by analyses of the clock mutant zonata: In this strain P1 could not be detected. An enzyme (Pz) was isolated which is serologically related to P2 but has a molecular weight of only 35000. Pz yields a broad band in disc electrophoresis and its K _m -value is tenfold increased as compared with the wildtype enzyme.Morphological and cytochemical similarities between the mutant zonata and wildtype mycelia displaying the action of heterogenic (vegetative) incompatibility (e. g. abnormal growth, free AP-activity in the cytoplasm) are discussed.

---

Abkürzungen AP Aminopeptidase - DE Diskelektrophorese - DFP Diisopropylfluorphosphat - IEF Isoelektrische Fokussierung - Hb Hämoglobin - Leu-4-NA Leucin-4-nitroanilid - Leu--NA Leucin--naphthylamid - MG Molekulargewicht - RSA Rinderserumalbumin - SDS Natriumdodecylsulfat Mit Unterstützung der Deutschen Forschungsgemeinschaft und des Landesamtes für Forschung (NRW).     

Mutations affecting meiosis in Podospora anserina

Forty mutants affecting meiosis and two affecting caryogamy were isolated in Podospora anserina. Growth and mitosis of these mutants were normal. Eighteen of them were studied by both light and electron microscopy so as to determine precisely how the behaviour of the chromosomes and/or the structure of the kinetic apparatus were altered.In the caryogamy-deficient mutants, the formation of crosiers is normal, but the nuclei of the apical cells never fuse. Three genes affect prophase I. For two of them the mutants are blocked before pachytene, the third being blocked between pachytene and diplotene. The other mutations concern the kinetic apparatus (centrosomal plaques, spindle) and the distribution of the nuclei in the spores.Some of these mutations are pleiotropic and also affect spore pigmentation, recombination frequency, and mutation rate.     

Rhythmisches Mycelwachstum bei Podospora anserina

The correlation between membrane structure and morphogenesis in fungi was examined by studying the effect of surface-active and membrane-altering substances upon the colonial shape of Podospora anserina. The following results were obtained:

1. The alcohols 1-propanol, 1-butanol and 1-octanol inhibited hyphal elongation and thus caused zonations in the wild strain. In the clock-mutant zonata, however, the zonations disappeared at high concentrations of the alcohols.
2. The detergents sodium-dodecylsulfate, sodium-desoxycholate, triton X-100 and brij-35 also induced zonations, i.e. rhythmic growth. Growing on complete media, the sensibility of the strains used was markedly reduced.
3. The antibiotics nonactin, nigericin and monensin, too, inhibited growth and caused zonations, which, however, were light dependent. In contrast, valinomycin inhibited the elongation of the hyphae only.

The results are discussed as consequences of alterations in structure and features of the membranes.     

Rhythmic mycelial growth in Podospora anserina

Summary Treatment of mycelial fragments with EMS and NMU yielded 15 revertants of the pleiotropic mutant zonata of Podospora anserina. Analysis by biological, biochemical and genetical methods has revealed that the reversions are caused by back mutation within the zonata locus. This leads to the conclusion that a point mutation causes the morphological and biochemical alterations in this mutant.A working hypothesis for the primary action of this gene and its significance for the elucidation of morphogenesis and of pleiotropism are discussed.With support of the Deutsche Forschungsgemeinschaft, Bad Godesberg (Germany).     

What triggers senescence in Podospora anserina?

Senescence of Podospora anserina is triggered by a cytoplasmic and infectious factor (the determinant of senescence) and is always correlated with mitochondrial DNA modifications, especially with the accumulation of small circular subgenomic DNA molecules, the senDNAs. Several observations have suggested that the senDNAs could be the cytoplasmic and infectious determinant. However, we show here (1) that senDNA molecules can be transferred to a young culture without the cotransmission of the determinant of senescence and (2) that the determinant of senescence does not segregate as a mitochondrial DNA mutation. Overall, our data strongly argue that amplification of senDNA molecules in the mitochondria is not an intrinsic property of these small DNA molecules. They question the nature of the actual determinant of senescence.     

Die Phenoloxydasen des Ascomyceten Podospora anserina

Summary Laccase of the wild strain of Podospora anserina was purified by subsequent treatment with protamine sulfate, precipitation with ammonium sulfate and column chromatography on DEAE-Sephadex and hydroxylapatite. The purity was confirmed by sedimentation and electrophoresis (molecular weight about 361 000, isoeletric point at pH 5.1).The blue-coloured pure laccase has its absorption-maxima at 280 and 605 m. The substrate specifity of the enzyme corresponds to results which have been earlier obtained with unpurified preparations (Esser 1963 b). Laccase is very temperature sensitive. It loses its activity after both freezing and heat treatment (half-life time at 60°C about 6 min). The Michaelis-constants as determined with Dopa, potassium ferrocyanide and catechol are in the range of 2 to 5·10^-3 Mol/l. The appropriate value for ascorbic acid is about 10^-2 less. The laccase contains about 12% carbohydrate and about 7,5% nitrogen. According to its copper content of 0.123% the laccase carries seven atoms of copper per molecule.

---

---

Teil I erschien in Arch. Mikrobiol. 46, 217–226 (1963).