Post-translational transport of proteins into microsomal membranes of Candida maltosa.

We have isolated from the yeast Candida maltosa microsomal membranes that are active in the translocation of proteins synthesized in cell-free systems derived from C. maltosa, Saccharomyces cerevisiae or wheat germ. Translocation and core glycosylation of prepro-alpha-factor, a secretory protein, were observed with yeast microsomes added during or after translation. The signal peptide is cleaved off. Cytochrome P-450 from C. maltosa, the first integral membrane protein studied in a yeast system, is also inserted both co- and post-translationally into Candida microsomal membranes. Its insertion into canine microsomes occurs efficiently only in a co-translational manner and is dependent on the function of the signal recognition particle.     

N-alkanes induce the synthesis of cytochrome P-450 mRNA in Candida maltosa

In the yeast Candida maltosa the level of cytochrome P-450 was 100-300-fold higher in alkane-grown cells than in glucose-grown ones (detected by a radioimmunoassay). It was shown immunochemically (1) that this was not the result of an assembly of preexisting apoenzyme with the prosthetic heme group. By cell-free translation of total poly(A)RNA in a wheat germ system and subsequent immunoprecipitation it was shown that the amount of mRNA coding for cytochrome P-450 paralleled its concentration in the cell.     

Increase in translatable mRNA for mitochondrial pyruvate carboxylase during differentiation of 3T3 preadipocytes

During differentiation of 3T3 preadipocytes into adipocytes the activity of pyruvate carboxylase, a key lipogenic enzyme, rises about 20-fold. This increase of enzymatic activity is correlated with a comparable rise in the rate of incorporation of [³⁵S]methionine into immunoadsorbable pyruvate carboxylase. Polyadenylated RNA, isolated from differentiated 3T3 adipocytes, directs the synthesis of pyruvate carboxylase in a messenger-dependent reticulocyte lysate translation system at a 18-fold greater rate than that isolated from undifferentiated cells. Thus, it appears that the differentiation-induced rise in the cellular level of pyruvate carboxylase results from an increased rate of carboxylase synthesis due to a rise in the level of translatable carboxylase messenger RNA.     

Studies of translatable mRNA for rabbit C-reactive protein.

C-reactive protein (CRP) mRNA was assayed by cell-free translation of poly(A)-containing liver RNA isolated both from rabbits stimulated to undergo the acute-phase response and from unstimulated control rabbits. No CRP-related translation products were identified until the denaturant methylmercury hydroxide (CH3HgOH) was added to the RNA before cell-free translation. In the presence of the denaturant, a 24000-Da translation product was synthesized which was immunochemically identifiable as the CRP primary translation product. It is likely that rabbit CRP mRNA can form a stable intramolecular duplex which interferes with its translatability in vitro. The 24000-Da CH3HgOH-facilitated cell-free translation product was not detected in poly(A)-containing liver RNA from unstimulated animals, indicating that the concentration of translatable CRP mRNA was dramatically induced during the acute-phase response. On the basis of absorption experiments, the 24000-Da CRP primary translation product was immunochemically more closely related to denatured CRP than to native CRP.     

Increase in the translatable mRNA for acetylcholine receptor during embryonic development of Torpedo ocellata electric organ

Single-turnover flash-induced ATP synthesis in chloroplasts was measured in situ with the luciferin luminescence method. In dark-adapted chloroplasts the first flashes only induce ATP hydrolysis. Once the reversible ATPase is fully activated, ATP hydrolysis persists for extended periods of darkness and flash-induced ATP-synthesis is optimal even at flash frequencies lower than 0.1 Hz. About one molecule of ATP is formed per 1000 chlorophyll and flash. In a low frequency flashing regime under steady state conditions, the newly formed ATP is stable. There is no threshold light intensity for flash-induced ATP synthesis. The data are in agreement with models involving short-range interaction between electron transport and the coupling factor.     

Fatty acid beta-oxidation system in microbodies of n-alkane-grown Candida tropicalis.

Localization of fatty acid beta-oxidation system in microbodies of Candida tropicalis cells growing on n-alkanes was studied. Microbodies isolated from the yeast cells showed palmitate-dependent activities of NAD reduction, acetyl-CoA formation and oxygen consumption. When sodium azide, an inhibitor of catalase, was added to the system, palmitate-dependent formation of hydrogen peroxide was observed. Stoichiometric study revealed that two moles of NAD were reduced per one mole of oxygen consumed in the absence of sodium azide and the presence of the inhibitor doubled the oxygen consumption by microbodies without an appreciable change in NAD reduction. These results indicate that the yeast microbodies contain beta-oxidation system of fatty acid, and that catalase located in the organelles participates in the degradation of hydrogen peroxide to be formed at the step of dehydrogenation of acyl-CoA.     

Isolation and characterization of major intrinsic microsomal membrane proteins.

Treatment of the membrane matrix derived from hepatic microsomes with buffered 1 M urea resulted in the selective extraction of a group of proteins together with a portion of the membrane lipid. Thorough chemical characterization of this fraction has been performed, and the proteins have been fractionated by two different procedures. The first of these, preparative polyacrylamide gel electrophoresis, has produced five highly homogeneous membrane proteins which have been characterized with regard to molecular weight, electrophoretic behavior in five different polyacrylamide systems, NH2 terminus, relative carbohydrate content, isoelectric point, and amino acid composition. The five proteins of this group fell in the molecular weight range of 54,000 to 96,000 and had isoelectric points ranging from pH 4.9 to pH 6.7. Further fractionation of the urea-soluble proteins by gel filtration in a sodium dodecyl sulfate-containing medium resulted in the isolation of four homogeneous molecular weight classes of proteins which have been characterized with respect to various physicochemical parameters. The major membrane glycoprotein (apparent molecular weight, 171,000) was isolated by this procedure and found to contain approximately equal amounts of NH2-terminal glycine and serine. suggesting the presence of at least two polypeptide chains in this molecular weight region. From the urea-insoluble fraction of the membrane comprising approximately 80% of the total protein, five intrinsic polypeptides designated S-5 through S-9 were isolated. S-5 (54,000) and S-6 (49,000) represent the most prominent components in the microsomal membrane, accounting for close to 30% of the total protein. Also isolated and characterized is the smallest membrane protein (S-9), a hydrophobic polypeptide of molecular weight 16,000. All of the urea-insoluble proteins are glycoproteins, and S-7 (35,000) gives the second most intense stain for carbohydrate of all proteins in the microsomal membrane.     

Mode of action of glyphosate in Candida maltosa

The broad-spectrum herbicide glyphosate inhibits the growth of Candida maltosa and causes the accumulation of shikimic acid and shikimate-3-phosphate. Glyphosate is a potent inhibitor of three enzymes of aromatic amino acid biosynthesis in this yeast. In relation to tyrosine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and dehydroquinate synthase, the inhibitory effect appears at concentrations in the mM range, but 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase is inhibited by micromolar concentrations of glyphosate. Inhibition of partially purified EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate (PEP) with a K _i -value of 12 M. The app. K _m for PEP is about 5-fold higher and was 62 M. Furthermore, the presence of glyphosate leads to derepression of many amino acid biosynthetic enzymes.Abbreviations DAHP 3-deoxy-D-arabino-heptulosonate 7-phosphate - EPSP synthase 5-enolpyruvylshikimate 3-phosphate synthase - PEP phosphoenolpyruvate - S-3-P shikimate-3-phosphate     

Molecular cloning of the Candida maltosa ADE1 gene.

The structural gene (ADE1) encoding phosphoribosyl-aminoimidazole-succinocarboxamide synthetase (SAICAR synthetase; EC 6.3.2.6) in Candida maltosa has been isolated by functional complementation of an ade1 strain of Saccharomyces cerevisiae. The gene was localized on a 2.5-kb BamHI DNA fragment. Nucleotide sequence analysis of the cloned gene has revealed an open reading frame encoding a protein (SAICAR synthetase) with an Mr of 32,751. The codon bias index, 0.68, indicates that the ADE1 gene is a moderately highly expressed gene. The cloned gene shows 63.5% nt identity and 65.2% deduced amino acid identity with the S. cerevisiae ADE1 gene which encodes the same enzymatic activity. The gene may be used as a convenient genetic marker for construction of a new host-vector system for C. maltosa.     

Potential Pathogenicity of Candida maltosa IAM 12248

The stereochemistry of (+)-(2Z,4E)-trans-1′,4′-dihydroxy-γ-ionylideneacetic acid, a major metabolite from Cercospora cruenta, a fungus found to produce (+)-abscisic acid, was reexamined as to its ¹H?¹H-Cosy and Noesy 2D-NMR spectra, and it was proved to have a chair conformation with an axial pentadienoate moiety. Further, the metabolism of (+)-[14C]-1′,4′-dihydroxy-γ-ionylideneacetic acid in tomato plants suggested the possibility of it being a biosynthetic intermediate of ABA in plants.     

The use of various mutagens for induction of nystatin-resistant mutants in Candida maltosa

The mutagenic activity of nitrous acid, 6-N-hydroxylaminopurine, N-methyl-N'-nitro-N-nitrosoguanidine and 4-N-nitroquinoline oxide was studied for Candida maltosa. The efficacy of their action on C. maltosa cells was determinded in order to obtain nystatin-resistant strains.     

Physiological and DNA characterization of Candida maltosa, a hydrocarbon-utilizing yeast.

Selected yeast classified as Candida sake van Uden et Buckley were examined for their physiological, morphological and immunological properties and their DNA relatedness. Candida maltosa Komagata, Nakase et Katsuya is herein recognized as a species separate from C. sake, Candida maltosa was distinguished from C. sake and from C. tropicalis by insignificant DNA reassociation. In addition, C. maltosa was distinguished from C. sake by its higher maximal growth temperature and lower guanine plus cytosine content of its DNA and from C. tropicalis by its failure to utilize soluble starch for growth and its resistance to cycloheximide. The species C. cloacae and C. subtropicalis are placed in synonymy with C. maltosa.     

Degradation of long-chain n-alkanes by the yeast Candida maltosa

Summary Microsomal membrane fractions of the yeast Candida maltosa were investigated with respect to their ability to catalyse the oxidation of n-alkanes, fatty alcohols and fatty acids. Analysis of intermediates of n-hexadecane oxidation led to the conclusion that monoterminal attack was predominant, whereas diterminal oxidation proceeded as a minor reaction. The oxidation of long-chain primary alcohols to the corresponding aldehydes occurred without addition of nicotinamide adenine dinucleotide (phosphate) [NAD(P)⁺] and was accompanied by stoichiometric oxygen consumption and hydrogen peroxide production, suggesting that an alcohol oxidase instead of an NAD(P)⁺-requiring alcohol dehydrogenase catalysed these reactions. As shown for n-hexadecane, the hydroxylation of palmitic acid was found to be carbon monoxide-dependent, indicating involvement of a cytochrome P-450 system, as in the case of n-alkane hydroxylation.     

Subcellular localization of long-chain alcohol dehydrogenase and aldehyde dehydrogenase in n-alkane-grown Candida tropicalis

Long-chain alcohol dehydrogenase and longchain aldehyde dehydrogenase were induced in the cells of Candida tropicalis grown on n-alkanes. Subcellular localization of these dehydrogenases, together with that of acyl-CoA synthetase and glycerol-3-phosphate acyltransferase, was studied in terms of the metabolism of fatty acids derived from n-alkane substrates. Both longchain alcohol and aldehyde dehydrogenases distributed in the fractions of microsomes, mitochondria and peroxisomes obtained from the alkane-grown cells of C. tropicalis. Acyl-CoA synthetase was also located in these three fractions. Glycerol-3-phosphate acyltransferase was found in microsomes and mitochondria, in contrast to fatty acid -oxidation system localized exclusively in peroxisomes. Similar results of the enzyme localization were also obtained with C. lipolytica grown on n-alkanes. These results suggest strongly that microsomal and mitochondrial dehydrogenases provide long-chain fatty acids to be utilized for lipid synthesis, whereas those in peroxisomes supply fatty acids to be degraded via -oxidation to yield energy and cell constituents.     

Presence of translatable mRNA in diapause eggs of Bombyx mori

Total RNA extracted from diapause eggs of Bombyx mori was found to be translatable in a cell-free heterologous protein synthesis system derived from wheat germ or rabbit reticulocyte lysate. This supports the idea that active mRNAs are contained in the polysomes of diapause eggs.     

Increase of a form of UDP-glucuronyltransferase glucuronizing various phenolic xenobiotics and the corresponding translatable mRNA in 3-methylcholanthrene-treated rat liver

Induction of hepatic microsomal UDP-glucuronyltransferase activity toward various phenolic xenobiotics by 3-methylcholanthrene treatment of rats was observed, and the process of the induction was studied. We had previously purified a form of UDP-glucuronyltransferase (called GT-1) having a catalytic activity toward phenolic xenobiotics from liver microsomes of 3-methylcholanthrene-treated rats. The antibodies against GT-1 inhibited the enzyme activity toward those xenobiotics in liver microsomes, and bound to a single protein having a molecular weight of about 54,000 Da (same value as that of GT-1) among microsomal proteins on immunoblotting analysis. The amount of GT-1 protein in hepatic microsomes was found to be increased in close correspondence with the activity increase by 3-methylcholanthrene treatment, by immunoblotting analysis using an uninducible cytochrome P-450 reductase as a negative standard. It was shown by in vitro translation assays that the protein increase described above resulted from the enhancement of the level of translatable mRNA encoding for GT-1. Increases in the amount of the protein immunochemically corresponding to GT-1 in the microsomes from liver of phenobarbital-treated rats and from extrahepatic organs, such as kidney, small intestine, and lung, of phenobarbital- or 3-methylcholanthrene-treated rats were also observed.