On the regulatory properties of a halophilic malic enzyme fromHalobacterium cutirubrum

Summary The NADP-linked malic enzyme fromHalobacterium cutirubrum is strongly inhibited by acetyl-CoA and NADH, and rather weakly inhibited by oxaloacetate and glyoxylate, in the presence of very high KCl concentrations (3,M), considered physiological for the extremely halophilic bacteria.This work was supported by grants from the consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, and the Consejo de Investigaciones de la Universidad Nacional de Rosario. JJC and MCV are members of the Carrera del Investigador Científico of the former and the latter institutions, respectively.     

Porphobilinogen-accumulation by a porphyrin auxotrophic strain ofBacillus subtilis

Summary The amount of porphobilinogen accumulated by aBacillus subtilis hemC mutant strain is dependent on time and exogenic aminolevulinic acid addition.hemC mutant seems to be suitable for porphobilinogen production on a large scale.Acknowledgments. We thank Prof. I. Bélàdi for renewing our interest in pophyrin auxotrophs and for her current help.     

Deletion mapping of a new gustatory mutant inDrosophila melanogaster

Summary A gustatory mutant ofDrosophila melanogaster insensitive to the taste of salt has been isolated. Genetic crosses and a deletion mapping analysis show that this mutation, designatedgust-M ₁ is located in the 93C_3–6-93D_6–7 region of the third chromosome.gust-M ₁ is also insensitive to the taste of quinine sulfate. The behavior of this mutant may be explained by assuming thatgust-M ₁ could be a mutation perturbing functions in the central nervous system affecting the responses to both compounds.     

Ammonia assimilatory enzymes in a nif−III mutant ofAzotobacter chroococcum

Summary The levels of ammonia assimilatory enzymes have been studied in a nif^–III mutant and a wild strain ofAzotobacter chroococcum grown in media containing different nitrogen sources. It is suggested that the nif^–III mutant may be defective in transport or incorporation of molybdenum.     

A blocked mutant ofClaviceps purpurea accumulating chanoclavine-I-aldehyde

Summary An alkaloid-blocked mutant ofClaviceps purpurea was isolated from a strain which produces ergotoxine alkaloids. The mutant accumulates chanoclavine-I and the corresponding aldehyde. It lacks the ability to form tetracyclic ergolines.Dedicated to Prof. Dr Dr h.c. K. Mothes on the occasion of his eightieth birthday.     

An increase in the influx of calcium ions into cilia induces thigmotaxis inParamecium caudatum

To understand the role of calcium ions in thigmotaxis inParamecium caudatum, the effects of caffeine, ruthenium red and lanthanum (LaCl₃) on thigmotaxis were examined. Thigmotaxis in the CNR mutant, which lacks voltage-dependent Ca²⁺-channels in the ciliary membrane, was also examined. Ruthenium red and LaCl₃ suppressed thigmotaxis inP. caudatum, while caffeine enhanced it. The CNR mutant showed hardly any thigmotaxis. It can be thought that an increase in Ca²⁺ influx and the intraciliary concentration of Ca²⁺ ions induces thigmotaxis inParamecium.     

Incorporation of photolabile azido fatty acid probes inNeurospora crassa andSaccharomyces cerevisiae

Summary Photolabile azido fatty acids supported the growth of fatty acid auxotrophs, thecel mutant ofNeurospora crassa and the KD115 mutant ofSaccharomyces cerevisiae. These fatty acids were incorporated into the membrane lipids of thecel and KD115 mutants, but were not used by the wild type strain.This work was presented at the 26th International Congress of Pure and Applied Chemistry, Session 1, Tokyo, September 4–10, 1977, abstracts p. 241.Support was provided by the Govt. of India to B.C. and by NCERT, New Delhi India to D.N.C.To whom requests for reprints should be sent.     

On the regulatory properties of a halophilic malic enzyme from Halobacterium cutirubrum.

The NADP-linked malic enzyme from Halobacterium cutirubrum is strongly inhibited by acetyl-CoA and NADH, and rather weakly inhibited by oxaloacetate and glyoxylate, in the presence of very high KCl concentrations (3 M), considered physiological for the extremely halophilic bacteria.     

Regulation of ppApp synthesis during sporulation of a conditionally asporogenous rifampin mutant ofBacillus subtilis

Summary The intracellular synthesis of ppApp in a conditionally asporogenous rifampin-resistant mutant ofBacillus subtilis stimulated to sporulate in the Sterlini-Mandelstam (SM) medium supplemented with ppApp is negligible and comparable to that of the non-sporulating culture. The formic acid extract from the sporulating culture stimulates sporulation of the mutant in SM medium.This paper was presented at the Annual Meeting of the American Society for Microbiology in Dallas, Texas, in March 1981. This work was supported in part by a grant from Research Corporation, New York, N.Y., USA.     

β-Lactamases as models for protein-folding studies

This review traces some of the key features of the folding of β-lactamases and their relevance to the way proteins fold in general. Studies on the enzymes have highlighted the nature and role of equilibrium and transient condensed states. The kinetics of folding are multiphasic, and when monitored by acrylamide quenching of the tryptophan fluorescence, an early phase provides evidence for the transient accumulation of a nonnative intermediate involving burial of tryptophan in a nonpolar environment. Intermediate phases can be understood in terms of progressive folding of different parts of the molecule. The later, slow phases are associated with proline isomerization in the TEM-1 enzyme and, in its P167T mutant form, with isomerization from trans to cis of the E166 T167 peptide bond. Coupled with kinetic and X-ray crystallographic studies of the β-lactamase from Staphylococcus aureus and its D179Q mutant, it appears that the final stage of folding is that of collapse and packing of the Ω-loop on to the main body of the protein.     

thiD locus ofEscherichia coli

Summary A mutant strain ofEscherichia coli K-12 lacking phosphomethylpyrimidine kinase activity was produced from the polyauxotrophic female strain, JC1552. The locus of its lesion, for which we propose the designationthiD, was mapped at about 46 min on the chromosome.     

The control of melanoblast differentiation in the periodic albino mutant ofXenopus

Summary Studies on the incidence of melanophores in older ventral trunk tissues and in isolated regions of periodic albino embryos ofXenopus suggest that melanin granule formation in mutant melanoblasts depends on an environmental contribution which arises at stage 43 in the endodermal tissues.     

Biosynthetic relationships among daunorubicin,doxorubicin and 13-dihydrodaunorubicin inStreptomyces peucetius

Summary By feeding¹⁴C-daunorubicin to a doxorubicin-producing mutant ofStreptomyces peucetius, labelled doxorubicin and 13-dihydrodaunorubicin have been obtained; this indicates that the former compound is a precursor of both the latter ones in the fermentation process.     

Thiamine-binding activity ofSaccharomyces cerevisiae plasma membrane

Summary The specific binding activity to [¹⁴C]thiamine was found to be located in the plasma membrane ofSaccharomyces cerevisiae. The activity was inhibited by several thiamine analogs and it was hardly detectable in the plasma membrane from a thiamine transport mutant ofSaccharomyces cerevisiae. Some properties of the thiamine-binding activity of yeast plasma membrane are discussed in connection with those of the thiamine transport system.     

Growth ofNostoc muscorum mutants in the presence of diuron (DCMU) and L-methionine-DL-sulfoximine

Summary Diuron (DCMU) is inhibitory to the photoautotrophic and photoheterotrophic growth of the N₂-fixing blue-green algaNostoc muscorum at concentrations of 1.0×10^–5 M and 2.0×10^–5 M, respectively. A mutant of this organism resistant to 5.0×10^–5 M DCMU under its photoheterotrophic growth conditions, with the ability to utilize DCMU as a carbon and nitrogen source for growth, and complete inability to grow photoautotrophically has been isolated. With the apparent defect in its photosynthetic ability, it is suggested that theDCMU ^r mutant lacks the step inhibited by 1.0×10^–5 M DCMU, and metabolizes DCMU by an existing enzyme system in the absence of such inhibition. That this enzyme may be glutamine synthetase (GS) is explained with the help of a L-methionine-DL-sulfoximine (MSO)-resistant mutant ofN. muscorum which is able to grow faster with 2.0×10^–5 DCMU and is known to contain an altered GS.Thanks are due to the Council of Scientific and Industrial Research, CSIR Complex, Govt. of India, New Delhi-110012, for appointing the author to the Scientists' Pool for undertaking researches on the physiological and genetic controls of nitrogen metabolism in blue-green algae, a part of which is presented in this literature.     

Etude immunochimique et électrophorétique de la conidiation deNeurospora crassa

Summary The antigens and soluble proteins ofNeurospora crassa wild-type and its conidiation deficient mutant amyc were analyzed by immunoelectrophoresis and acrylamide gel electrophoresis respectively. Comparison of the patterns of the soluble proteins of the 2 strains, obtained with both techniques, showed an alteration of antigens and proteins in the mutant. A specific antigenic protein present in the wild-type, presumably in connection with conidiation, was also found in the mutant amyc when it was induced to form conidia.     

Regular oscillations in suspensions of a putatively chaotic mutant ofDictyostelium discoideum

Summary We have tested the light-scattering properties of suspensions of theDictyostelium discoideum mutantHH201 derived from the mutantFr17. Previous studies indicated thatHH201 andFr17 possess highly irregular rhythmic properties which might represent aperiodic oscillations, i.e. chaos. We report that the former mutant can display regular oscillatory behavior. Possible explanations for this result are discussed, including that of a transition from chaotic to periodic behavior resulting from some parameter change or from strong intercellular coupling in cell suspensions.     

Temperature-dependent responses to a developmental gradient in theDrosophila wing

Summary The mutant hairy (h) increases the number of sensillae on theDrosophila wing. This allows us to quantify a gradient that determines the type of sense organ that forms along the third long vein. Temperature significantly shifts the positional responses to this underlying gradient.This research was supported by National Science Foundation grant BSR-8300025. We thank Laura Karcher for the figure.     

A spontaneous benomyl-resistant mutant ofPodospora anserina exhibiting a diurnal growth rhythm

Summary A spontaneous mutant ofP. anserina isolated by screening for benomyl resistance exhibited a diurnal growth rhythm dependent on light-dark cycles. The rhythmic character, the benomyl resistance and a growth rate reduced to 50% of that of the wild type were inherited together over more than 10 generations. The locus was mapped on linkage group II, 0.35 map units distal to the locusz (=0.81 map units from the centromere).     

Unstable genetic system inDrosophila melanogaster: I. Instability at theCinnabar locus

Summary A mutant strain containing acinnabar allele (cn ^rbr ,rojo brillante) is reported, that produces wild-type revertants at thecinnabar (cn) locus. Incn ^rbr /cn heterozygotes the rate of mutation is highly increased. The presence of a mutator agent acting premeiotically is indicated.D.L. Lindsley and E.H. Grell, Genetic variations ofDrosophila melanogaster. Carnegie Institution of Washington, Washington, 1968; Publication No. 627.