Wally H. Müller
Utrecht University
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Wally H. Müller.
Molecular Microbiology | 2002
Johan C. Kapteyn; Lois L. Hoyer; J. E. Hecht; Wally H. Müller; A. Andel; Arie J. Verkleij; Marja Makarow; H. van den Ende; Frans M. Klis
In Candida albicans wild‐type cells, the β1,6‐glucanase‐extractable glycosylphosphatidylinositol (GPI)‐dependent cell wall proteins (CWPs) account for about 88% of all covalently linked CWPs. Approximately 90% of these GPI‐CWPs, including Als1p and Als3p, are attached via β1,6‐glucan to β1,3‐glucan. The remaining GPI‐CWPs are linked through β1,6‐glucan to chitin. The β1,6‐glucanase‐resistant protein fraction is small and consists of Pir‐related CWPs, which are attached to β1,3‐glucan through an alkali‐labile linkage. Immunogold labelling and Western analysis, using an antiserum directed against Saccharomyces cerevisiae Pir2p/Hsp150, point to the localization of at least two differentially expressed Pir2 homologues in the cell wall of C. albicans. In mnn9Δ and pmt1Δ mutant strains, which are defective in N‐ and O‐glycosylation of proteins respectively, we observed enhanced chitin levels together with an increased coupling of GPI‐CWPs through β1,6‐glucan to chitin. In these cells, the level of Pir‐CWPs was slightly upregulated. A slightly increased incorporation of Pir proteins was also observed in a β1,6‐glucan‐deficient hemizygous kre6Δ mutant. Taken together, these observations show that C. albicans follows the same basic rules as S. cerevisiae in constructing a cell wall and indicate that a cell wall salvage mechanism is activated when Candida cells are confronted with cell wall weakening.
The EMBO Journal | 1991
Wally H. Müller; T.P. van der Krift; A. J. J. Krouwer; Han A. B. Wösten; L. H. M. Van Der Voort; Erik B. Smaal; Arie J. Verkleij
The localization of the enzymes involved in penicillin biosynthesis in Penicillium chrysogenum hyphae has been studied by immunological detection methods in combination with electron microscopy and cell fractionation. The results suggest a complicated pathway involving different intracellular locations. The enzyme delta‐(L‐alpha‐aminoadipyl)‐L‐cysteinyl‐D‐valine synthetase was found to be associated with membranes or small organelles. The next enzyme isopenicillin N‐synthetase appeared to be a cytosolic enzyme. The enzyme which is involved in the last step of penicillin biosynthesis, acyltransferase, was located in organelles with a diameter of 200–800 nm. These organelles, most probably, are microbodies. A positive correlation was found between the capacity for penicillin production and the number of organelles per cell when comparing different P. chrysogenum strains.
Studies in Mycology | 2013
Pauline Krijgsheld; Robert-Jan Bleichrodt; G.J. van Veluw; Fengfeng Wang; Wally H. Müller; Jan Dijksterhuis; Han A. B. Wösten
The genus Aspergillus represents a diverse group of fungi that are among the most abundant fungi in the world. Germination of a spore can lead to a vegetative mycelium that colonizes a substrate. The hyphae within the mycelium are highly heterogeneous with respect to gene expression, growth, and secretion. Aspergilli can reproduce both asexually and sexually. To this end, conidiophores and ascocarps are produced that form conidia and ascospores, respectively. This review describes the molecular mechanisms underlying growth and development of Aspergillus.
Biochimica et Biophysica Acta | 1992
Wally H. Müller; Roelof A.L. Bovenberg; Marloes H. Groothuis; Fred Kattevilder; Erik B. Smaal; Lucia H.M. Van der Voort; Arie J. Verkleij
Penicillium chrysogenum strains were constructed which express a mutant acyltransferase lacking the putative targeting signal for microbody proteins. The mutated enzyme was located in vacuoles and in neighbouring cytoplasm. Although acyltransferase was expressed in vivo and was active in vitro, the mutants did not produce penicillin. The results demonstrate the involvement of microbodies in penicillin production.
Molecular Microbiology | 1993
Leon G. J. Frenken; J. Wil Bos; Chris Visser; Wally H. Müller; Jan Tommassen; C. Theo Verrips
Pseudomonas glumae PG1 is able to secrete lipase into the extracellular medium. The lipase is produced as a precursor protein, with an N‐terminal signal sequence. A second open reading frame (ORF) was found immediately downstream of the lipase structural gene, lip A, a situation found for the lipases of some other Pseudomonas species. Inactivation of this ORF resulted in a lipase‐negative phenotype, indicating its importance in the production of active extracellular lipase. The ORF, lipB, potentially encodes a protein of 353‐amtno‐acid residues, having a hydrophobic N‐terminal (amino acids 1 to 90) and a hydrophilic C‐terminal part. As a first step in determining the role of LipB, its subcellular location was determined. The protein was found to fractionate with the inner membranes. The expression of fusions of lipB fragments with phoA revealed an Nin–Cout topology for the LipB protein, which was confirmed by protease accessibility studies on EDTA‐permeabilized cells and on inverted inner membrane vesicles. These and other results indicate that most of the LipB polypeptide is located in the periplasm and anchored to the inner membrane by an an N‐terminal transmembrane helix, located between amino acids 19 and 40.
Applied and Environmental Microbiology | 2000
C. Sagt; Bertrand Kleizen; René Verwaal; M. D. M. de Jong; Wally H. Müller; A. Smits; C. Visser; Johannes Boonstra; Arie J. Verkleij; C. T. Verrips
ABSTRACT Saccharomyces cerevisiae is often used to produce heterologous proteins that are preferentially secreted to increase economic feasibility. We used N-glycosylation as a tool to enhance protein secretion. Secretion of cutinase, a lipase, and llama VHH antibody fragments by S. cerevisiae orPichia pastoris improved following the introduction of an N-glycosylation site. When we introduced an N-glycosylation consensus sequence in the N-terminal region of a hydrophobic cutinase, secretion increased fivefold. If an N-glycosylation site was introduced in the C-terminal region, however, secretion increased only 1.8-fold. These results indicate that the use of N glycosylation can significantly enhance heterologous protein secretion.
Journal of Bacteriology | 2005
Hans de Haard; Sandra Bezemer; Aat M. Ledeboer; Wally H. Müller; Piet J. Boender; Sylvain Moineau; Marie-Cecile Coppelmans; Arie J. Verkleij; Leon G. J. Frenken; C. Theo Verrips
Bacteriophage p2 belongs to the most prevalent lactococcal phage group (936) responsible for considerable losses in industrial production of cheese. Immunization of a llama with bacteriophage p2 led to higher titers of neutralizing heavy-chain antibodies (i.e., devoid of light chains) than of the classical type of immunoglobulins. A panel of p2-specific single-domain antibody fragments was obtained using phage display technology, from which a group of potent neutralizing antibodies were identified. The antigen bound by these antibodies was identified as a protein with a molecular mass of 30 kDa, homologous to open reading frame 18 (ORF18) of phage sk1, another 936-like phage for which the complete genomic sequence is available. By the use of immunoelectron microscopy, the protein is located at the tip of the tail of the phage particle. The addition of purified ORF18 protein to a bacterial culture suppressed phage infection. This result and the inhibition of cell lysis by anti-ORF18 protein antibodies support the conclusion that the ORF18 protein plays a crucial role in the interaction of bacteriophage p2 with the surface receptors of Lactococcus lactis.
Current Biology | 2011
Kalika Prasad; Stephen P. Grigg; Michalis Barkoulas; Ram Kishor Yadav; Gabino F. Sanchez-Perez; Violaine Pinon; Ikram Blilou; Hugo Hofhuis; Pankaj Dhonukshe; Carla Galinha; Ari Pekka Mähönen; Wally H. Müller; Smita Raman; Arie J. Verkleij; Berend Snel; G. Venugopala Reddy; Miltos Tsiantis; Ben Scheres
The pattern of plant organ initiation at the shoot apical meristem (SAM), termed phyllotaxis, displays regularities that have long intrigued botanists and mathematicians alike. In the SAM, the central zone (CZ) contains a population of stem cells that replenish the surrounding peripheral zone (PZ), where organs are generated in regular patterns. These patterns differ between species and may change in response to developmental or environmental cues [1]. Expression analysis of auxin efflux facilitators of the PIN-FORMED (PIN) family combined with modeling of auxin transport has indicated that organ initiation is associated with intracellular polarization of PIN proteins and auxin accumulation [2-10]. However, regulators that modulate PIN activity to determine phyllotactic patterns have hitherto been unknown. Here we reveal that three redundantly acting PLETHORA (PLT)-like AP2 domain transcription factors control shoot organ positioning in the model plant Arabidopsis thaliana. Loss of PLT3, PLT5, and PLT7 function leads to nonrandom, metastable changes in phyllotaxis. Phyllotactic changes in plt3plt5plt7 mutants are largely attributable to misregulation of PIN1 and can be recapitulated by reducing PIN1 dosage, revealing that PLT proteins are key regulators of PIN1 activity in control of phyllotaxis.
Fungal Genetics and Biology | 2009
Denise I. Jacobs; Maurien Olsthoorn; Isabelle Maillet; Michiel Akeroyd; Stefaan Breestraat; Serge Petrus Donkers; Rob van der Hoeven; Cees A. M. J. J. van den Hondel; Rolf Kooistra; Thomas Lapointe; Hildegard Menke; Rogier Meulenberg; Marijke Misset; Wally H. Müller; Noël N. M. E. van Peij; Arthur F. J. Ram; Sabrina Rodriguez; Marc S. Roelofs; Johannes Andries Roubos; Marcel van Tilborg; Arie J. Verkleij; Herman Jan Pel; Hein Stam; C. Sagt
The filamentous fungus Aspergillus niger is widely exploited for industrial production of enzymes and organic acids. An integrated genomics approach was developed to determine cellular responses of A. niger to protein production in well-controlled fermentations. Different protein extraction methods in combination with automated sample processing and protein identification allowed quantitative analysis of 898 proteins. Three different enzyme overproducing strains were compared to their isogenic fungal host strains. Clear differences in response to the amount and nature of the overproduced enzymes were observed. The corresponding genes of the differentially expressed proteins were studied using transcriptomics. Genes that were up-regulated both at the proteome and transcriptome level were selected as leads for generic strain improvement. Up-regulated proteins included proteins involved in carbon and nitrogen metabolism as well as (oxidative) stress response, and proteins involved in protein folding and endoplasmic reticulum-associated degradation (ERAD). Reduction of protein degradation through the removal of the ERAD factor doaA combined with overexpression of the oligosaccharyl transferase sttC in A. niger overproducing beta-glucuronidase (GUS) strains indeed resulted in a small increase in GUS expression.
Microscopy Research and Technique | 1998
Bruno M. Humbel; Margo D.M. de Jong; Wally H. Müller; Arie J. Verkleij
For scarce antigens or antigens which are embedded in a dense macromolecular structure, on‐section labeling, the first method of choice, is not always successful. Often, the antigen can be localized by immunofluorescence microscopy, usually by a pre‐embedding labeling method. Most of these methods lead to loss of ultrastructural details and, hence, labeling at electron microscope resolution does not add essential information. The scope of this paper is to compare five permeabilization methods for pre‐embedding labelling for electron microscopy. We aim for a method that is easy to use and suitable for routine investigations. For our ongoing work, special attention is given to labeling of the cell nucleus. Accessibility of cytoplasmic and nuclear antigens is monitored with a set of different marker antibodies.