Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Hansenula polymorpha  (17)
  • 21.60.Ev  (3)
  • Organic Chemistry  (3)
  • 1
    ISSN: 1617-4623
    Keywords: Peroxisomes ; Targeting signals ; Yeast ; Hansenula polymorpha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dihydroxyacetone synthase (DAS) and methanol oxidase (MOX) are the major enzyme constituents of the peroxisomal matrix in the methylotrophic yeast Hansenula polymorpha when grown on methanol as a sole carbon source. In order to characterize their topogenic signals the localization of truncated polypeptides and hybrid proteins was analysed in transformed yeast cells by subcellular fractionation and electron microscopy. The C-terminal part of DAS, when fused to the bacterial β-lactamase or mouse dihydrofolate reductase, directed these hybrid polypeptides to the peroxisome compartment. The targeting signal was further delimited to the extreme C-terminus, comprising the sequence N-K-L-COOH, similar to the recently identified and widely distributed peroxisomal targeting signal (PTS) S-K-L-COOH in firefly luciferase. By an identical approach, the extreme C-terminus of MOX, comprising the tripeptide A-R-F-COOH, was shown to be the PTS of this protein. Furthermore, on fusion of a C-terminal sequence from firefly luciferase including the PTS, β-lactamase was also imported into the peroxisomes of H. polymorpha. We conclude that, besides the conserved PTS (or described variants), other amino acid sequences with this function have evolved in nature.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0749-503X
    Keywords: alcohol oxidase ; flavin adenine dinucleotide ; peroxisomes ; Hansenula polymorpha ; protein translocation ; protein assembly ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the role of flavin adenine dinucleotide (FAD) in the in vivo assembly of peroxisomal alcohol oxidase (AO) in the yeast Hansenula polymorpha. In previous studies, using a riboflavin (Rf) autotrophic mutant, an unequivocal judgement could not be made, since Rf-limitation led to a partial block of AO import in this mutant. This resulted in the accumulation of AO precursors in the cytosol where they remained separated from the putative peroxisomal AO assembly factors. In order to circumvent the peroxisomal membrane barrier, we have now studied AO assembly in a peroxisome-deficient/Rf-autotrophic double mutant (Δper1.rif1) of H. polymorpha. By sucrose density centrifugation and native gel electrophoresis, three conformations of AO were detected in crude extracts of Δper1.rif1 cells grown under Rf-limitation, namely active octameric AO and two inactive, monomeric forms. One of the latter forms lacked FAD; this form was barely detectable in extracts wild-type and Δper1 cells, but had accumulated in the cytosol of rif1 cells. The second form of monomeric AO contained FAD; this form was also present in Δper1 cells but absent/very low in wild-type and rif1 cells. In vivo only these FAD-containing monomers associate into the active, octameric protein. We conclude that in H. polymorpha FAD binding to the AO monomer is mediated by a yet unknown peroxisomal factor and represents the crucial and essential step to enable AO oligomerization; the actual octamerization and the eventual crystallization in peroxisomes most probably occurs spontaneously.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0749-503X
    Keywords: peroxisome biogenesis ; peroxisomal protein import ; peroxisomal membrane protein ; PEX gene regulation ; Hansenula polymorpha ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: PEX3 encodes a 52 kDa peroxisomal membrane protein (PMP), essential for peroxisome biogenesis in the yeast Hansenula polymorpha. The relation between Pex3p levels and peroxisome formation was studied in wild type (WT) and Δpex3 strains expressing additional copies of PEX3 under control of a substrate-inducible promoter, namely the strong alcohol oxidase (PAOX) or the weaker amine oxidase (PAMO) promoter. In glucose-grown Δpex3 cells, containing PAOX. PEX3, Pex3p was undetectable and peroxisomes were absent. After induction of these cells on methanol, peroxisomes were rapidly formed. At Pex3p levels up to 7-10 times the values observed in WT controls normal peroxisomes were present. However, at further enhanced Pex3p levels a general matrix protein import defect was observed. This phenomenon was paralleled by aberrant peroxisome assembly and the formation of numerous small vesicles. These vesicles contained Pex3p, together with other H. polymorpha PMPs, but lacked the major matrix proteins which has accumulated in the cytosol. The implications of our results on PEX3 gene regulation and functioning of the peroxisomal matrix protein import machinery in H. polymorpha are discussed. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 23.60.+e ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nuclei221Ra and217Rn have been investigated in the α-decay chain225Th→221Ra →217Rn through γ-ray and conversion-electron studies. The short-lived225Th nuclei (T 1/2=8min) were produced in the226Ra(α, 5n) reaction, and γ-rays and conversion electrons were measured — between the irradiation periods — in coincidence with αparticles. In221Ra the five lowest levels are interpreted as members of aK=5/2 paritydoublet with ΔEπ=104 keV. These levels, as well as a higher-lying Kπ=3/2+ band, are consistent with an octupole deformation of221Ra, as expected from theoretical considerations. In217Rn only three excited levels are observed, with a favoured α-decay to a 5/2+ excited level thus establishing positive parity for the ground state of221Ra.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Positive and negative parity bands have been followed up to 10+ (possibly 12+) and 11− in224Ra and are compared to the corresponding bands in the isotone226Th. If a constant value of the intrinsic quadrupole moment is assumed for allE2 transitions in224Ra theE1/E2 branching ratios are consistent with an intrinsic dipole moment of ¦Q1¦=0.032(3)e·fm. This small value, as compared to ¦Q1¦=0.30(2)e·fm for226Th, can be explained by an almost complete cancellation of large positive liquid-drop and negative shell-model contributions.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Cyanide Ions with α,β-Unsaturated Esters, IV1,2,3). - Reactions to CarbocyclesSodium cyanide reacts with diethyl 2-methylenealkanedioates 1a-c and 8a-h to give simple or alkylated ethyl 2-cyano-3-oxo-1-cycloalkanecarboxylates 5a-c and 9a-h, respectively. From these the 3-oxo-1-cycloalkanecarboxylic acids 6a-c and 10a-h, respectively, and the methyl esters 11a-h are obtained. Analogously α,β-unsaturated dicarboxylates such as 12a, b lead to ethyl 2-cyano-2-methyl-5-oxo-1-cyclopentanecarboxylate (13a) and ethyl 2-cyano-2-methyl-6-oxo-1-cyclohexanecarboxylate (13b), respectively.
    Notes: Einwirkung von Natriumcyanid auf 2-Methylenalkandisäure-diethylester 1a-c und 8a-h führt zu einfachen bzw. alkylierten 2-Cyan-3-oxo-1-cycloalkancarbonsäure-ethylestern 5a-c und 9a-h. Daraus erhält man die 3-Oxo-1-cycloalkancarbonsäuren 6a-c und 10a-h sowie die Methylester 11a-h. Analog reagieren α,β-ungesättigte Dicarbonsäureester wie 12a, b zum 2-Cyan-2-methyl-5-oxo-1-cyclopentancarbonsäure-ethylester (13a) bzw. 2-Cyan-2-methyl-6-oxo-1-cyclo-hexancarbonsäure-ethylester (13b).
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Cyanide Ions with α,β-Unsaturated Esters, V1). - Reactions Leading to Affiliation of CarbocyclesSodium cyanide reacts with the unsaturated diesters 4-6 under aprotic conditions (DMSO) to give the bicycles 7-9. These are easily transformed into the acids 10-12 and the methyl esters 13-15. Reaction with unsaturated esters like 16, 18 leads to the bicyclic compounds with bridged atoms 17, 19.
    Notes: Natriumcyanid reagiert mit den ungesättigten Di-Estern 4-6 unter aprotischen Bedingungen (DMSO) zu den Bicyclen 7-9. Diese lassen sich leicht in die Säuren 10-12 sowie in die Ester 13-15 überführen. Bei Verwendung von ungesättigten Estern des Typs 16, 18 entstehen bicyclische Verbindungen mit Brückenkohlenstoffatomen 17, 19.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 6 (1990), S. 87-97 
    ISSN: 0749-503X
    Keywords: Hansenula polymorpha ; methylotrophic yeast ; microbodies ; peroxisome-deficient mutants ; alcohol oxidase ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: As a first step in a genetic approach towards understanding peroxisome biogenesis and function, we have sought to isolate mutants of the methylotrophic yeast Hansenula polymorpha which are deficient in peroxisomes. A collection of 260 methanol-utilization-defective strains was isolated and screened for the ability to utilize a second compound, ethanol, the metabolism of which involves peroxisomes. Electron microscopical investigations of ultrathin sections of selected pleiotropic mutants revealed two strains which were completely devoid of peroxisomes. In both, different peroxisomal matrix enzymes were active but located in the cytosol; these included catalase, alcohol oxidase, malate synthase and isocitrate lyase.Subsequent backcrossing experiments revealed that for all crosses involving both strains, the methanol- and ethanol utilizing-deficient phenotypes segregated independently of each other, indicating that different gene mutations were responsible for these phenotypes. The phenotype of the backcrossed peroxisome-deficient derivates was identical: defective in the ability to utilize methanol but capable of growth on other carbon sources, including ethanol.The mutations complemented and therefore were recessive mutations in different genes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0749-503X
    Keywords: Hansenula polymorpha ; alcohol oxidase ; amine oxidase ; choline ; peroxisome-deficient mutant ; enzyme assembly ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the expression of alcohol oxidase (AO) in a peroxisome-deficient mutant strain of Hansenula polymorpha. High levels of octameric, active AO (up to 3·0 U/mg protein) were detected in cells grown at low dilution rates in a glucose-limited chemostat in the presence of choline as the sole nitrogen source. Monomeric or other intermediate forms of AO were not detected in the mutant strain. This indicated that assembly of the protein into active octameric molecules in the cytosol was as efficient as in wild-type cells where this process is confined to the peroxisomal matrix. At relatively low rates of expression (less than 1 U/mg protein) AO was localized throughout the cytosol and, surprisingly, was also present inside the nucleus. However, at enhanced levels large crystalloids were formed. Generally one crystalloid was observed per cell, whereas smaller ones were occasionally found in developing buds. Also large crystalloids have been observed inside the nucleus. These crystalloids were not surrounded by a membrane. Based on the morphology of the molecules that constituted these crystalloids and the results of (immuno)cytochemical experiments we conclude that the crystalloids are composed of octameric AO molecules, arranged in a regular lattice, identical to the 3-dimensional architecture previously described for the crystalline matrix of peroxisomes in methanol-grown wild type cells of H. polymorpha. Attempts to purify the crystalloids by conventional fractionation methods failed, due to their apparent fragility; however, (immuno)cytochemical experiments revealed that catalase and dihydroxyacetone synthase were also associated with these structures.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...