Yeast Protein Research Articles

The yeast protein Ure2p triggers Tau pathology in a mouse model of tauopathy

The molecular mechanisms that trigger Tau aggregation in Alzheimer's disease (AD) remain elusive. Fungi, especially Saccharomyces cerevisiae (S.cerevisiae), can be found in brain samples from patients with AD. Here, we show that the yeast protein Ure2p from S.cerevisiae interacts with Tau and facilitates its aggregation. The Ure2p-seeded Tau fibrils are more potent in seeding Tau and causing neurotoxicity invitro. When injected into the hippocampus of Tau P301S transgenic mice, the Ure2p-seeded Tau fibrils show enhanced seeding activity compared with pure Tau fibrils. Strikingly, intracranial injection of Ure2p fibrils promotes the aggregation of Tau and cognitive impairment in Tau P301S mice. Furthermore, intranasal infection of S.cerevisiae in the nasal cavity of Tau P301S mice accelerates the aggregation of Tau. Together, these observations indicate that the yeast protein Ure2p initiates Tau pathology. Our results provide a conceptual advance that non-mammalian prions may cross-seed mammalian prion-like proteins.

An Evolutionary-Based Mutation With Functional Annotation to Identify Protein Complexes Within PPI Networks

The research deals with an evolutionary-based mutation with functional annotation to identify protein complexes within PPI networks. An important field of research in computational biology is the difficult and fundamental challenge of revealing complexes in protein interaction networks. The complex detection models that have been developed to tackle challenges are mostly dependent on topological properties and rarely use the biological properties of PPI networks. This research aims to push the evolutionary algorithm to its maximum by employing gene ontology (GO) to communicate across proteins based on biological information similarity for direct genes. The outcomes show that the suggested method can be utilized to improve the predictability of the complexes identified. The GO functional annotation of proteins as a heuristic guide is injected into the framework of single-objective evolutionary algorithms (EAs), while the complex detection community score (CS) model works as a fitness function in EAs. In the experiments, we analyzed the performance of our proposed algorithm when applied to the publicly accessible yeast protein networks. The results show a considerable improvement in the detection ability of complexes in the PPI network.

Tld1 is a regulator of triglyceride lipolysis that demarcates a lipid droplet subpopulation.

Cells store lipids in the form of triglyceride (TG) and sterol ester (SE) in lipid droplets (LDs). Distinct pools of LDs exist, but a pervasive question is how proteins localize to and convey functions to LD subsets. Here, we show that the yeast protein YDR275W/Tld1 (for TG-associated LD protein 1) localizes to a subset of TG-containing LDs and reveal it negatively regulates lipolysis. Mechanistically, Tld1 LD targeting requires TG, and it is mediated by two distinct hydrophobic regions (HRs). Molecular dynamics simulations reveal that Tld1's HRs interact with TG on LDs and adopt specific conformations on TG-rich LDs versus SE-rich LDs in yeast and human cells. Tld1-deficient yeast display no defect in LD biogenesis but exhibit elevated TG lipolysis dependent on lipase Tgl3. Remarkably, overexpression of Tld1, but not LD protein Pln1/Pet10, promotes TG accumulation without altering SE pools. Finally, we find that Tld1-deficient cells display altered LD mobilization during extended yeast starvation. We propose that Tld1 senses TG-rich LDs and regulates lipolysis on LD subpopulations.

Optimization of Brewer's Yeast Quantity in Liquid and Gel Larval Diets for the Mediterranean Fruit Fly.

Several artificial larval diets have been developed, evaluated and used for mass-rearing of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Teprhitidae). There are several efforts to reduce the cost of rearing and optimize the quality of the produced sterile males that are destined for release in sterile insect release programs. Survival, growth, longevity and reproductive capacity of sterile males are strongly connected with the most expensive ingredient, the brewer's yeast (protein), in the larval diet. The current study focused on settling the optimal content of brewer's yeast in a liquid diet and a gel diet. Egg hatch rates, developmental duration of immatures, pupation rate, pupae and adult survival were recorded as indicators of quantity and quality of the produced adults. Egg hatch was higher and larval developmental duration longer in the gel diet. In contrast to the liquid diet, an increase in brewer's yeast concentration was correlated with increased pupation rate and pupae survival in the gel diet. Reducing brewer's yeast up to 50% of its initial quantity had no significant effect on the survival of the emerging adults regardless of the diet type. Our findings may contribute to the production of low-cost and effective diets for use in mass-rearing facilities of medflies.

Enhanced O/W emulsion stability and betanin protection using yeast protein and chitooligosaccharide: Comparative insights from complex coacervation and layer-by-layer methods

Emulsions play a pivotal role in food and related industries, yet oil-in-water (O/W) emulsions, a staple emulsion, are plagued by instability issues like aggregation, flocculation, and gravitational separation during storage. Stabilizing these emulsions has often involved the use of proteins or polysaccharides. Within this context, this research delves into comparing two distinctive stabilization strategies for emulsions. The yeast protein (YP), chitooligosaccharide (COS), and betanin were employed to formulate a complexation emulsion (CE) using a complex coacervation method, and a bilayer emulsion (BE) through a layer-by-layer method. The effects of these divergent methods on the emulsion's physicochemical properties, microscopic structure, and the stability of betanin was assessed. The findings indicate that the yeast protein-chitooligosaccharide-betanin (YCB) emulsion prepared using the layer-by-layer method demonstrated the smallest droplet size and the greatest absolute ζ-potential. After a storage period of seven days, this emulsion showed the lowest emulsification index, indicating excellent storage stability. In tandem, an increase in apparent viscosity was observed, with the emulsion exhibiting weak gel-like behavior. The incorporation of betanin has improved the physical stability of emulsions, and concurrently, the emulsion presented an improved storage stability of betanin. These results provide insightful perspectives for the development of emulsions based on bilayer interfaces, contributing to the expansion of novel fungal protein applications in the fields of emulsion technology, food processing, and the stabilization of bioactive molecules.

Secretory production of 7-dehydrocholesterol by engineered Saccharomyces cerevisiae.

7-Dehydrocholesterol (7-DHC) can be directly converted to vitamin D3 by UV irradiation and de novo synthesis of 7-DHC in engineered Saccharomyces cerevisiae has been recognized as an attractive substitution to traditional chemical synthesis. Introduction of sterol extracellular transport pathway for the secretory production of 7-DHC is a promising approach to achieve higher titer and simplify the downstream purification processing. A series of genes involved in ergosterol pathway were combined reinforced and reengineered in S. cerevisiae. A biphasic fermentation system was introduced and 7-DHC was found to be enriched in oil-phase with an increased titer by 1.5-folds. Quantitative PCR revealed that say1, atf2, pdr5, pry1-3 involved in sterol storage and transport were all significantly induced in sterol overproduced strain. To enhance the secretion capacity, lipid transporters of pathogen-related yeast proteins (Pry), Niemann-Pick disease type C2 (NPC2), ATP-binding cassette (ABC)-family, and their homologues were screened. Both individual and synergetic overexpression of Plant pathogenesis Related protein-1 (Pr-1) and Sterol transport1 (St1) largely increased the de novo biosynthesis and secretory productivity of 7-DHC, and the final titer reached 28.2mgg-1 with a secretion ratio of 41.4%, which was 26.5-folds higher than the original strain. In addition, the cooperation between Pr-1 and St1 in sterol transport was further confirmed by confocal microscopy, molecular docking, and directed site-mutation. Selective secretion of different sterol intermediates was characterized in sterol over-produced strain and the extracellular export of 7-DHC developed in present study significantly improved the cell biosynthetic capacity, which offered a novel modification idea for 7-DHC de novo biosynthesis by S. cerevisiae cell factory.

Slow-digestive yeast protein concentrate: An investigation of its in vitro digestibility and digestion behavior

Yeast protein concentrate, a by-product of the fermentation industry waste, is a potential alternative protein source with high nutritional quality, environmental sustainability, and functional properties. However, its digestibility and digestion behavior are poorly understood. In this study, we compared the in vitro digestion behavior of yeast protein concentrate and whey protein concentrate using simulated gastrointestinal conditions. We found that yeast protein concentrate had lower digestibility than whey protein concentrate (31.25% vs. 86.23% at 120 min of pepsin digestion and 75.12% vs. 95.2% at 120 min of pancreatin digestion). Yeast protein concentrate differed from whey protein concentrate in microstructure, secondary structure, and amino acid composition, which may affect its digestion behavior. Compared to whey protein concentrate, a higher level of β-sheets and a lower zeta potential explain the slow-digesting property of yeast protein concentrate. Yeast protein concentrate also underwent depolymerization and Plastein reaction during digestion. These results provided valuable information for developing and applying yeast protein concentrate as an alternative to conventional animal protein.

The Intrinsically Disordered N Terminus in Atg12 from Yeast Is Necessary for the Functional Structure of the Protein.

The Atg12 protein in yeast is an indispensable polypeptide in the highly conserved ubiquitin-like conjugation system operating in the macroautophagy/autophagy pathway. Atg12 is covalently conjugated to Atg5 through the action of Atg7 and Atg10; the Atg12-Atg5 conjugate binds Atg16 to form an E3 ligase that functions in a separate conjugation pathway involving Atg8. Atg12 is comprised of a ubiquitin-like (UBL) domain preceded at the N terminus by an intrinsically disordered protein region (IDPR), a domain that comprises a major portion of the protein but remains elusive in its conformation and function. Here, we show that the IDPR in unconjugated Atg12 is positioned in proximity to the UBL domain, a configuration that is important for the functional structure of the protein. A major deletion in the IDPR disrupts intactness of the UBL domain at the unconjugated C terminus, and a mutation in the predicted α0 helix in the IDPR prevents Atg12 from binding to Atg7 and Atg10, which ultimately affects the protein function in the ubiquitin-like conjugation cascade. These findings provide evidence that the IDPR is an indispensable part of the Atg12 protein from yeast.

The Thermal Properties and Nutritional Value of Biomass of Oleaginous Yeast Rhodotorula sp. during Glucose Fed-Batch Cultivation in Medium with Waste Nitrogen

The biotechnological processing of oleaginous yeast biomass should be comprehensively managed using the zero-waste policy. This study focused on the biomass of the red yeast Rhodotorula obtained from a medium containing waste nitrogen. The cells accumulate lipids in intracellular lipid droplets; however, they are also rich in protein. Therefore, the nutritional value of lipid and protein, according to their fatty acid and amino acid composition, is a necessary step for practical application. For the very first time, this study focused on understanding the influence of temperature on powdered red yeast biomass to study components phase transition or chemical reactions by using DSC. Rhodotorula glutinis var. rubescens was cultivated in a glucose fed-batch in a potato wastewater medium, where the biomass yield was powdered, and lipid and fatty acid, protein, and amino acid compositions were determined. The DSC diagrams of red yeast biomass were characterized by two small and mild endothermic peaks, indicating the presence of fat and the presence of low molecular weight carbohydrates and a distinct peak associated with the presence of crystalline sugars. The nutritional quality of the lipid fraction as atherogenicity (0.223), thrombogenicity index (0.438), PUFA/SFA (0.24), and the n-6/n-3 ratio (3.275) was adequate for the recommendation and resulted from the fatty acid composition. The yeast protein was characterized by a high content of glutamic acid (99 mg/1 g of protein), and a value of essential amino acid index of protein suggested a superior amino acid composition compared to the FAO/WHO standard. Despite a high essential amino acid index (>120), yeast protein was characterized by a low content of Lys or Met.

Characterization of the RAD52 Gene in the Budding Yeast Naumovozyma castellii.

Several sources of DNA damage compromise the integrity and stability of the genome of every organism. Specifically, DNA double-strand breaks (DSBs) can have lethal consequences for the cell. To repair this type of DNA damage, the cells employ homology-directed repair pathways or non-homologous end joining. Homology-directed repair requires the activity of the RAD52 epistasis group of genes. Rad52 is the main recombination protein in the budding yeast Saccharomyces cerevisiae, and rad52Δ mutants have been characterized to show severe defects in DSB repair and other recombination events. Here, we identified the RAD52 gene in the budding yeast Naumovozyma castellii. Our analysis showed that the primary amino acid sequence of N. castellii Rad52 shared 70% similarity with S. cerevisiae Rad52. To characterize the gene function, we developed rad52Δ mutant strains by targeted gene replacement transformation. We found that N. castellii rad52Δ mutants showed lowered growth capacity, a moderately altered cell morphology and increased sensitivity to genotoxic agents. The decreased viability of the N. castellii rad52Δ mutants in the presence of genotoxic agents indicates that the role of the Rad52 protein in the repair of DNA damage is conserved in this species.

Broad functional profiling of fission yeast proteins using phenomics and machine learning.

Many proteins remain poorly characterized even in well-studied organisms, presenting a bottleneck for research. We applied phenomics and machine-learning approaches with Schizosaccharomyces pombe for broad cues on protein functions. We assayed colony-growth phenotypes to measure the fitness of deletion mutants for 3509 non-essential genes in 131 conditions with different nutrients, drugs, and stresses. These analyses exposed phenotypes for 3492 mutants, including 124 mutants of 'priority unstudied' proteins conserved in humans, providing varied functional clues. For example, over 900 proteins were newly implicated in the resistance to oxidative stress. Phenotype-correlation networks suggested roles for poorly characterized proteins through 'guilt by association' with known proteins. For complementary functional insights, we predicted Gene Ontology (GO) terms using machine learning methods exploiting protein-network and protein-homology data (NET-FF). We obtained 56,594 high-scoring GO predictions, of which 22,060 also featured high information content. Our phenotype-correlation data and NET-FF predictions showed a strong concordance with existing PomBase GO annotations and protein networks, with integrated analyses revealing 1675 novel GO predictions for 783 genes, including 47 predictions for 23 priority unstudied proteins. Experimental validation identified new proteins involved in cellular aging, showing that these predictions and phenomics data provide a rich resource to uncover new protein functions.

Broad functional profiling of fission yeast proteins using phenomics and machine learning

Many proteins remain poorly characterized even in well-studied organisms, presenting a bottleneck for research. We applied phenomics and machine-learning approaches with Schizosaccharomyces pombe for broad cues on protein functions. We assayed colony-growth phenotypes to measure the fitness of deletion mutants for 3509 non-essential genes in 131 conditions with different nutrients, drugs, and stresses. These analyses exposed phenotypes for 3492 mutants, including 124 mutants of ‘priority unstudied’ proteins conserved in humans, providing varied functional clues. For example, over 900 proteins were newly implicated in the resistance to oxidative stress. Phenotype-correlation networks suggested roles for poorly characterized proteins through ‘guilt by association’ with known proteins. For complementary functional insights, we predicted Gene Ontology (GO) terms using machine learning methods exploiting protein-network and protein-homology data (NET-FF). We obtained 56,594 high-scoring GO predictions, of which 22,060 also featured high information content. Our phenotype-correlation data and NET-FF predictions showed a strong concordance with existing PomBase GO annotations and protein networks, with integrated analyses revealing 1675 novel GO predictions for 783 genes, including 47 predictions for 23 priority unstudied proteins. Experimental validation identified new proteins involved in cellular aging, showing that these predictions and phenomics data provide a rich resource to uncover new protein functions.

Redox-mediated activation of ATG3 promotes ATG8 lipidation and autophagy progression in Chlamydomonas reinhardtii.

Autophagy is one of the main degradative pathways used by eukaryotic organisms to eliminate useless or damaged intracellular material to maintain cellular homeostasis under stress conditions. Mounting evidence indicates a strong interplay between the generation of reactive oxygen species and the activation of autophagy. Although a tight redox regulation of autophagy has been shown in several organisms, including microalgae, the molecular mechanisms underlying this control remain poorly understood. In this study, we have performed an in-depth in vitro and in vivo redox characterization of ATG3, an E2-activating enzyme involved in ATG8 lipidation and autophagosome formation, from 2 evolutionary distant unicellular model organisms: the green microalga Chlamydomonas (Chlamydomonas reinhardtii) and the budding yeast Saccharomyces cerevisiae. Our results indicated that ATG3 activity from both organisms is subjected to redox regulation since these proteins require reducing equivalents to transfer ATG8 to the phospholipid phosphatidylethanolamine. We established the catalytic Cys of ATG3 as a redox target in algal and yeast proteins and showed that the oxidoreductase thioredoxin efficiently reduces ATG3. Moreover, in vivo studies revealed that the redox state of ATG3 from Chlamydomonas undergoes profound changes under autophagy-activating stress conditions, such as the absence of photoprotective carotenoids, the inhibition of fatty acid synthesis, or high light irradiance. Thus, our results indicate that the redox-mediated activation of ATG3 regulates ATG8 lipidation under oxidative stress conditions in this model microalga.

The Dictyostelium discoideum FimA protein, unlike yeast and plant fimbrins, is regulated by calcium similar to mammalian plastins

Plastins, also known as fimbrins, are highly conserved eukaryotic multidomain proteins that are involved in actin-bundling. They all contain four independently folded Calponin Homology-domains and an N-terminal headpiece that is comprised of two calcium-binding EF-hand motifs. Since calcium-binding has been shown to be integral to regulating the activity of the three mammalian plastin proteins, we decided to study the properties of the headpiece regions of fimbrins from the model plant Arabidopsis thaliana, the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the amoeba Dictyostelium discoideum. Of these protein domains only the FimA headpiece from the amoeba protein possesses calcium binding properties. Structural characterization of this protein domain by multidimensional NMR and site-directed mutagenesis studies indicates that this EF-hand region of FimA also contains a regulatory ‘switch helix’ that is essential to regulating the activity of the human L-plastin protein. Interestingly this regulatory helical region seems to be lacking in the plant and yeast proteins and in fimbrins from all other nonmotile systems. Typical calmodulin antagonists can displace the switch-helix from the FimA headpiece, suggesting that such drugs can deregulate the Ca2+-regulation of the actin-bunding in the amoeba, thereby making it a useful organism for drug screening against mammalian plastins.

A3DyDB: exploring structural aggregation propensities in the yeast proteome

BackgroundThe budding yeast Saccharomyces cerevisiae (S. cerevisiae) is a well-established model system for studying protein aggregation due to the conservation of essential cellular structures and pathways found across eukaryotes. However, limited structural knowledge of its proteome has prevented a deeper understanding of yeast functionalities, interactions, and aggregation.ResultsIn this study, we introduce the A3D yeast database (A3DyDB), which offers an extensive catalog of aggregation propensity predictions for the S. cerevisiae proteome. We used Aggrescan 3D (A3D) and the newly released protein models from AlphaFold2 (AF2) to compute the structure-based aggregation predictions for 6039 yeast proteins. The A3D algorithm exploits the information from 3D protein structures to calculate their intrinsic aggregation propensities. To facilitate simple and intuitive data analysis, A3DyDB provides a user-friendly interface for querying, browsing, and visualizing information on aggregation predictions from yeast protein structures. The A3DyDB also allows for the evaluation of the influence of natural or engineered mutations on protein stability and solubility. The A3DyDB is freely available at http://biocomp.chem.uw.edu.pl/A3D2/yeast.ConclusionThe A3DyDB addresses a gap in yeast resources by facilitating the exploration of correlations between structural aggregation propensity and diverse protein properties at the proteome level. We anticipate that this comprehensive database will become a standard tool in the modeling of protein aggregation and its implications in budding yeast.

Evolution and functional diversification of yeast sugar transporters.

While simple sugars such as monosaccharides and disaccharide are the typical carbon source for most yeasts, whether a species can grow on a particular sugar is generally a consequence of presence or absence of a suitable transporter to enable its uptake. The most common transporters that mediate sugar import in yeasts belong to the major facilitator superfamily (MFS). Some of these, for example the Saccharomyces cerevisiae Hxt proteins have been extensively studied, but detailed information on many others is sparce. In part, this is because there are many lineages of MFS transporters that are either absent from, or poorly represented in, the model S. cerevisiae, which actually has quite a restricted substrate range. It is important to address this knowledge gap to gain better understanding of the evolution of yeasts and to take advantage of sugar transporters to exploit or engineer yeasts for biotechnological applications. This article examines the full repertoire of MFS proteins in representative budding yeasts (Saccharomycotina). A comprehensive analysis of 139 putative sugar transporters retrieved from 10 complete genomes sheds new light on the diversity and evolution of this family. Using the phylogenetic lens, it is apparent that proteins have often been misassigned putative functions and this can now be corrected. It is also often seen that patterns of expansion of particular genes reflects the differential importance of transport of specific sugars (and related molecules) in different yeasts, and this knowledge also provides an improved resource for the selection or design of tailored transporters.

A 3D printed plastic frame deeply impacts yeast cell growth.

Solid State Fermentation (SSF) processes have been explored for yeast growth and protein and metabolites production. However, most of these processes lack standardization. In this work, we present a polylactic acid (PLA) 3D printed matrix that dramatically enhances yeast growth when embedded in liquid media compared to equivalent static cultures, and changes yeast expression patterns at the proteome level (data are available via ProteomeXchange with identifier PXD043759). Moreover, differences in sugar assimilation and ethanol production, as the main product of alcoholic fermentation, are observed. Our results suggest that these matrixes may be useful for a vast range of biotechnological applications based on yeast fermentation.

Phylogeny of PmCCD Gene Family and Expression Analysis of Flower Coloration and Stress Response in Prunus mume.

The CCD gene family plays a crucial role in the cleavage of carotenoids, converting them into apocarotenoids. This process not only impacts the physiology and development of plants but also enhances their tolerance toward different stresses. However, the character of the PmCCD gene family and its role in ornamental woody Prunus mume remain unclear. Here, ten non-redundant PmCCD genes were identified from the P. mume genome, and their physicochemical characteristics were predicted. According to the phylogenetic tree, PmCCD proteins were classified into six subfamilies: CCD1, CCD4, CCD7, CCD8, NCED and CCD-like. The same subfamily possessed similar gene structural patterns and numbers of conserved motifs. Ten PmCCD genes were concentrated on three chromosomes. PmCCD genes exhibited interspecific collinearity with P. armeniaca and P. persica. Additionally, PmCCD genes had obvious specificity in different tissues and varieties. Compared with white-flowered 'ZLE', PmCCD1 and PmCCD4 genes were low-expressed in 'HJH' with yellow petals, which suggested PmCCD1 and PmCCD4 might be related to the formation of yellow flowers in P. mume. Nine PmCCD genes could respond to NaCl or PEG treatments. These genes might play a crucial role in salt and drought resistance in P. mume. Moreover, PmVAR3 and PmSAT3/5 interacted with PmCCD4 protein in yeast and tobacco leaf cells. This study laid a foundation for exploring the role of the PmCCD gene family in flower coloration and stress response in P. mume.

The Properties and Domain Requirements for Phase Separation of the Sup35 Prion Protein In Vivo.

The Sup35 prion protein of budding yeast has been reported to undergo phase separation to form liquid droplets both at low pH in vitro and when energy depletion decreases the intracellular pH in vivo. It also has been shown using purified proteins that this phase separation is driven by the prion domain of Sup35 and does not re-quire its C-terminal domain. In contrast, we now find that a Sup35 fragment consisting of only the N-terminal prion domain and the M-domain does not phase separate in vivo; this phase separation of Sup35 requires the C-terminal domain, which binds Sup45 to form the translation termination complex. The phase-separated Sup35 not only colocalizes with Sup45 but also with Pub1, a stress granule marker protein. In addition, like stress granules, phase separation of Sup35 appears to require mRNA since cycloheximide treatment, which inhibits mRNA release from ribosomes, prevents phase separation of Sup35. Finally, unlike Sup35 in vitro, Sup35 condensates do not disassemble in vivo when the intracellular pH is increased. These results suggest that, in energy-depleted cells, Sup35 forms supramolecular assemblies that differ from the Sup35 liquid droplets that form in vitro.

Identification and immunogenic potential of glycosylphosphatidylinositol-anchored proteins in Paracoccidioides brasiliensis.

In fungal pathogens the cell wall plays an important role in host-pathogen interactions because its molecular components (e.g., polysaccharides and proteins) may trigger immune responses during infection. GPI-anchored proteins represent the main protein class in the fungal cell wall where they can perform several functions, such as cell wall remodeling and adhesion to host tissues. Genomic analysis has identified the complement of GPI-anchored proteins in many fungal pathogens, but the function has remained unknown for most of them. Here, we conducted an RNA expression analysis of GPI-anchored proteins of Paracoccidioides brasiliensis which causes paracoccidioidomycosis (PCM), an important human systemic mycosis endemic in Latin America. The expression of the GPI-anchored proteins was analyzed by quantitative PCR in both the mycelium and yeast forms. qPCR analysis revealed that the transcript levels of 22 of them were increased in hyphae and 10 in yeasts, respectively, while 14 did not show any significant difference in either form. Furthermore, we cloned 46 open reading frames and purified their corresponding GPI-anchored proteins in the budding yeast. Immunoblot and ELISA analysis of four purified GPI-anchored proteins revealed immune reactivity of these proteins against sera obtained from PCM patients. The information obtained in this study provides valuable information about the expression of many GPI-anchored proteins of unknown function. In addition, based on our immune analysis, some GPI-anchored proteins are expressed during infection and therefore, they might serve as good candidates for the development of new diagnostic methods.