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Peng H, Darlington APS, South EJ, Chen HH, Jiang W, Ledesma-Amaro R. A molecular toolkit of cross-feeding strains for engineering synthetic yeast communities. Nat Microbiol 2024; 9:848-863. [PMID: 38326570 PMCID: PMC10914607 DOI: 10.1038/s41564-023-01596-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 12/18/2023] [Indexed: 02/09/2024]
Abstract
Engineered microbial consortia often have enhanced system performance and robustness compared with single-strain biomanufacturing production platforms. However, few tools are available for generating co-cultures of the model and key industrial host Saccharomyces cerevisiae. Here we engineer auxotrophic and overexpression yeast strains that can be used to create co-cultures through exchange of essential metabolites. Using these strains as modules, we engineered two- and three-member consortia using different cross-feeding architectures. Through a combination of ensemble modelling and experimentation, we explored how cellular (for example, metabolite production strength) and environmental (for example, initial population ratio, population density and extracellular supplementation) factors govern population dynamics in these systems. We tested the use of the toolkit in a division of labour biomanufacturing case study and show that it enables enhanced and tuneable antioxidant resveratrol production. We expect this toolkit to become a useful resource for a variety of applications in synthetic ecology and biomanufacturing.
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Affiliation(s)
- Huadong Peng
- Department of Bioengineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Alexander P S Darlington
- Warwick Integrative Synthetic Biology Centre, School of Engineering, University of Warwick, Coventry, UK
| | - Eric J South
- Molecular Biology, Cell Biology and Biochemistry Program, Boston University, Boston, MA, USA
| | - Hao-Hong Chen
- Department of Bioengineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China
| | - Wei Jiang
- Department of Bioengineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Rodrigo Ledesma-Amaro
- Department of Bioengineering, Imperial College London, London, UK.
- Imperial College Centre for Synthetic Biology, Imperial College London, London, UK.
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2
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Hart SFM, Chen CC, Shou W. Pleiotropic mutations can rapidly evolve to directly benefit self and cooperative partner despite unfavorable conditions. eLife 2021; 10:57838. [PMID: 33501915 PMCID: PMC8184212 DOI: 10.7554/elife.57838] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 01/26/2021] [Indexed: 01/08/2023] Open
Abstract
Cooperation, paying a cost to benefit others, is widespread. Cooperation can be promoted by pleiotropic ‘win-win’ mutations which directly benefit self (self-serving) and partner (partner-serving). Previously, we showed that partner-serving should be defined as increased benefit supply rate per intake benefit. Here, we report that win-win mutations can rapidly evolve even under conditions unfavorable for cooperation. Specifically, in a well-mixed environment we evolved engineered yeast cooperative communities where two strains exchanged costly metabolites, lysine and hypoxanthine. Among cells that consumed lysine and released hypoxanthine, ecm21 mutations repeatedly arose. ecm21 is self-serving, improving self’s growth rate in limiting lysine. ecm21 is also partner-serving, increasing hypoxanthine release rate per lysine consumption and the steady state growth rate of partner and of community. ecm21 also arose in monocultures evolving in lysine-limited chemostats. Thus, even without any history of cooperation or pressure to maintain cooperation, pleiotropic win-win mutations may readily evolve to promote cooperation.
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Affiliation(s)
| | - Chi-Chun Chen
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, Seattle, United States
| | - Wenying Shou
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, Seattle, United States.,University College London, Department of Genetics, Evolution and Environment, Centre for Life's Origins and Evolution (CLOE), London, United Kingdom
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3
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Hart SFM, Pineda JMB, Chen CC, Green R, Shou W. Disentangling strictly self-serving mutations from win-win mutations in a mutualistic microbial community. eLife 2019; 8:e44812. [PMID: 31162049 PMCID: PMC6548503 DOI: 10.7554/elife.44812] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 03/19/2019] [Indexed: 12/31/2022] Open
Abstract
Mutualisms can be promoted by pleiotropic win-win mutations which directly benefit self (self-serving) and partner (partner-serving). Intuitively, partner-serving phenotype could be quantified as an individual's benefit supply rate to partners. Here, we demonstrate the inadequacy of this thinking, and propose an alternative. Specifically, we evolved well-mixed mutualistic communities where two engineered yeast strains exchanged essential metabolites lysine and hypoxanthine. Among cells that consumed lysine and released hypoxanthine, a chromosome duplication mutation seemed win-win: it improved cell's affinity for lysine (self-serving), and increased hypoxanthine release rate per cell (partner-serving). However, increased release rate was due to increased cell size accompanied by increased lysine utilization per birth. Consequently, total hypoxanthine release rate per lysine utilization (defined as 'exchange ratio') remained unchanged. Indeed, this mutation did not increase the steady state growth rate of partner, and is thus solely self-serving during long-term growth. By extension, reduced benefit production rate by an individual may not imply cheating.
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Affiliation(s)
| | | | - Chi-Chun Chen
- Division of Basic SciencesFred Hutchinson Cancer Research CenterSeattleUnited States
| | - Robin Green
- Division of Basic SciencesFred Hutchinson Cancer Research CenterSeattleUnited States
| | - Wenying Shou
- Division of Basic SciencesFred Hutchinson Cancer Research CenterSeattleUnited States
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4
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Hart SFM, Mi H, Green R, Xie L, Pineda JMB, Momeni B, Shou W. Uncovering and resolving challenges of quantitative modeling in a simplified community of interacting cells. PLoS Biol 2019; 17:e3000135. [PMID: 30794534 PMCID: PMC6402699 DOI: 10.1371/journal.pbio.3000135] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 03/06/2019] [Accepted: 01/18/2019] [Indexed: 12/22/2022] Open
Abstract
Quantitative modeling is useful for predicting behaviors of a system and for rationally constructing or modifying the system. The predictive power of a model relies on accurate quantification of model parameters. Here, we illustrate challenges in parameter quantification and offer means to overcome these challenges, using a case example in which we quantitatively predict the growth rate of a cooperative community. Specifically, the community consists of two Saccharomyces cerevisiae strains, each engineered to release a metabolite required and consumed by its partner. The initial model, employing parameters measured in batch monocultures with zero or excess metabolite, failed to quantitatively predict experimental results. To resolve the model-experiment discrepancy, we chemically identified the correct exchanged metabolites, but this did not improve model performance. We then remeasured strain phenotypes in chemostats mimicking the metabolite-limited community environments, while mitigating or incorporating effects of rapid evolution. Almost all phenotypes we measured, including death rate, metabolite release rate, and the amount of metabolite consumed per cell birth, varied significantly with the metabolite environment. Once we used parameters measured in a range of community-like chemostat environments, prediction quantitatively agreed with experimental results. In summary, using a simplified community, we uncovered and devised means to resolve modeling challenges that are likely general to living systems.
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Affiliation(s)
- Samuel F. M. Hart
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Hanbing Mi
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Robin Green
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Li Xie
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Jose Mario Bello Pineda
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Babak Momeni
- Department of Biology, Boston College, Boston, Massachusetts, United States of America
| | - Wenying Shou
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
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5
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Denton JA, Gokhale CS. Synthetic Mutualism and the Intervention Dilemma. Life (Basel) 2019; 9:E15. [PMID: 30696090 PMCID: PMC6463046 DOI: 10.3390/life9010015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 01/09/2019] [Accepted: 01/23/2019] [Indexed: 01/09/2023] Open
Abstract
Ecosystems are complex networks of interacting individuals co-evolving with their environment. As such, changes to an interaction can influence the whole ecosystem. However, to predict the outcome of these changes, considerable understanding of processes driving the system is required. Synthetic biology provides powerful tools to aid this understanding, but these developments also allow us to change specific interactions. Of particular interest is the ecological importance of mutualism, a subset of cooperative interactions. Mutualism occurs when individuals of different species provide a reciprocal fitness benefit. We review available experimental techniques of synthetic biology focused on engineered synthetic mutualistic systems. Components of these systems have defined interactions that can be altered to model naturally occurring relationships. Integrations between experimental systems and theoretical models, each informing the use or development of the other, allow predictions to be made about the nature of complex relationships. The predictions range from stability of microbial communities in extreme environments to the collapse of ecosystems due to dangerous levels of human intervention. With such caveats, we evaluate the promise of synthetic biology from the perspective of ethics and laws regarding biological alterations, whether on Earth or beyond. Just because we are able to change something, should we?
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Affiliation(s)
- Jai A Denton
- Genomics and Regulatory Systems Unit, Okinawa Institute of Science and Technology, Onna-son 904-0412, Japan.
| | - Chaitanya S Gokhale
- Research Group for Theoretical models of Eco-Evolutionary Dynamics, Max Planck Institute for Evolutionary Biology, 24304 Plön, Germany.
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6
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Daignan-Fornier B, Pinson B. Yeast to Study Human Purine Metabolism Diseases. Cells 2019; 8:E67. [PMID: 30658520 PMCID: PMC6356901 DOI: 10.3390/cells8010067] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 01/15/2019] [Accepted: 01/15/2019] [Indexed: 02/04/2023] Open
Abstract
Purine nucleotides are involved in a multitude of cellular processes, and the dysfunction of purine metabolism has drastic physiological and pathological consequences. Accordingly, several genetic disorders associated with defective purine metabolism have been reported. The etiology of these diseases is poorly understood and simple model organisms, such as yeast, have proved valuable to provide a more comprehensive view of the metabolic consequences caused by the identified mutations. In this review, we present results obtained with the yeast Saccharomyces cerevisiae to exemplify how a eukaryotic unicellular organism can offer highly relevant information for identifying the molecular basis of complex human diseases. Overall, purine metabolism illustrates a remarkable conservation of genes, functions and phenotypes between humans and yeast.
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Affiliation(s)
- Bertrand Daignan-Fornier
- Université de Bordeaux IBGC UMR 5095 1, rue Camille Saint-Saëns, F-33077 Bordeaux, France.
- Centre National de la Recherche Scientifique IBGC UMR 5095 1, rue Camille Saint-Saëns, F-33077 Bordeaux, France.
| | - Benoît Pinson
- Université de Bordeaux IBGC UMR 5095 1, rue Camille Saint-Saëns, F-33077 Bordeaux, France.
- Centre National de la Recherche Scientifique IBGC UMR 5095 1, rue Camille Saint-Saëns, F-33077 Bordeaux, France.
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7
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Abstract
Heterotypic cooperation—two populations exchanging distinct benefits that are costly to produce—is widespread. Cheaters, exploiting benefits while evading contribution, can undermine cooperation. Two mechanisms can stabilize heterotypic cooperation. In ‘partner choice’, cooperators recognize and choose cooperating over cheating partners; in ‘partner fidelity feedback’, fitness-feedback from repeated interactions ensures that aiding your partner helps yourself. How might a spatial environment, which facilitates repeated interactions, promote fitness-feedback? We examined this process through mathematical models and engineered Saccharomyces cerevisiae strains incapable of recognition. Here, cooperators and their heterotypic cooperative partners (partners) exchanged distinct essential metabolites. Cheaters exploited partner-produced metabolites without reciprocating, and were competitively superior to cooperators. Despite initially random spatial distributions, cooperators gained more partner neighbors than cheaters did. The less a cheater contributed, the more it was excluded and disfavored. This self-organization, driven by asymmetric fitness effects of cooperators and cheaters on partners during cell growth into open space, achieves assortment. DOI:http://dx.doi.org/10.7554/eLife.00960.001 Cooperation between individuals of the same species, and also between different species, is known to be important in evolution. Large fish, for example, rely on small cleaner fish to remove parasites, while the small fish benefit from the nutrients in these parasites. However, cooperation can be undermined by other individuals or species who “cheat” by taking advantage of those who cooperate, without providing any benefits in return. For example, some cleaner fish cheat by biting off healthy tissue from their host, in addition to parasites. Genetically-related individuals who cooperate by sharing identical benefits can combat cheaters by giving preferential treatment to their relatives (a process known as kin discrimination) or by staying close to the relatives to form clusters (kin fidelity). However, two genetically-unrelated populations that mutually cooperate by sharing different benefits cannot employ these methods to overcome cheaters. Instead they rely on either partner choice or partner fidelity feedback. Partner choice – the approach adopted by cleaner fish and their hosts – relies on one population recognizing a signal from the other population and responding accordingly: for example, large fish observe cleaner fish and approach those that cooperate with their current host and avoid those that cheat. Partner fidelity feedback, on the other hand, relies on repeated interactions between the two populations providing an advantage in terms of evolutionary fitness to both: for example, organelles called mitochondria and chloroplasts live inside cells, helping the cells to harvest energy and providing energy for themselves and the host cells in the process. In some cases – such as the cooperation between figs and fig wasps, or between certain plants and the bacteria that fix nitrogen in their roots – researchers cannot agree if the populations are relying on partner choice or partner fidelity feedback. Now Momeni et al. have used a combination of experiments on yeast and mathematical modeling to explore partner fidelity feedback in greater detail. They started by using genetic engineering techniques to produce two species of yeast that mutually cooperate, each providing a metabolite that is essential to the other, but are not able to recognize each other: this means that these populations cannot rely on partner choice to combat cheaters. Momeni et al. then observed how these two species interacted with each other and a third species of yeast that cheated by consuming one of the metabolites without releasing any metabolite of its own. Momeni et al. found that as long as there was space for the yeast cells to grow into, the two species that cooperated self-organized into mixed clusters, with the cheating species being excluded from these clusters. The self-organization was driven by a positive feedback loop involving the two species that cooperated, with each species helping to increase the fitness of the other. The results of Momeni et al. demonstrate that it is possible for two genetically unrelated populations to cooperate and combat cheaters without the use of partner choice. DOI:http://dx.doi.org/10.7554/eLife.00960.002
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Affiliation(s)
- Babak Momeni
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
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8
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Adaptation to a new environment allows cooperators to purge cheaters stochastically. Proc Natl Acad Sci U S A 2012; 109:19079-86. [PMID: 23091010 DOI: 10.1073/pnas.1210190109] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cooperation via production of common goods is found in diverse life forms ranging from viruses to social animals. However, natural selection predicts a "tragedy of the commons": Cheaters, benefiting from without producing costly common goods, are more fit than cooperators and should destroy cooperation. In an attempt to discover novel mechanisms of cheater control, we eliminated known ones using a yeast cooperator-cheater system engineered to supply or exploit essential nutrients. Surprisingly, although less fit than cheaters, cooperators quickly dominated a fraction of cocultures. Cooperators isolated from these cocultures were superior to the cheater isolates they had been cocultured with, even though these cheaters were superior to ancestral cooperators. Resequencing and phenotypic analyses revealed that evolved cooperators and cheaters all harbored mutations adaptive to the nutrient-limited cooperative environment, allowing growth at a much lower concentration of nutrient than their ancestors. Even after the initial round of adaptation, evolved cooperators still stochastically dominated cheaters derived from them. We propose the "adaptive race" model: If during adaptation to an environment, the fitness gain of cooperators exceeds that of cheaters by at least the fitness cost of cooperation, the tragedy of the commons can be averted. Although cooperators and cheaters sample from the same pool of adaptive mutations, this symmetry is soon broken: The best cooperators purge cheaters and continue to grow, whereas the best cheaters cause rapid self-extinction. We speculate that adaptation to changing environments may contribute to the persistence of cooperative systems before the appearance of more sophisticated mechanisms of cheater control.
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9
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Gots JS, Benson CE, Jochimsen B, Koduri KR. Microbial models and regulatory elements in the control of purine metabolism. CIBA FOUNDATION SYMPOSIUM 2008:23-41. [PMID: 204462 DOI: 10.1002/9780470720301.ch3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Bacterial systems have been used to identify and characterize the organization of the genetic units and the regulatory elements that control purine metabolism. An analysis of 13 genes that control the biosynthesis of AMP and GMP has revealed three multigenic operons. These show properties of gene contiguity, promoter sites, coordinate expression and polarity effects. The unit controlling the formation of IMP is one operon (pur JHD) consisting of three genes which together control the formation of phosphoribosylglycinamide synthetase (EC 6.3.4.13), an early enzyme in the biosynthetic pathway, and a terminal bifunctional complex (IMP cyclohydrolase--formyltransferase). Regulatory mutants were isolated and characterized by several methods including the use of a unique fusion of two unrelated operons. Both operator constitutive and repressor type (purR) mutations have been identified. The purR product functions in the common control of several genetically distinct enzymes that participate before the formation of IMP. Plasmid DNA enriched for the purE operon has been isolated and used in the study of the role of nucleotide effectors in the binding of repressor-like proteins. AMP but not GMP is needed for binding, and purR mutants are deficient in the binding substance. Mutants with differential blocks in the salvage and interconverting reactions have been used to characterize the regulatory elements of the formation and the activity of guanosine kinase, GMP reductase (EC 1.6.6.8), and purine nucleoside phosphorylase (EC 2.4.2.1). Two structural gene products (purF) and (purG) have been implicated as possible regulatory elements for the use of guanosine, and a role for glutamine in the induction of GMP reductase has been revealed.
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Shou W, Ram S, Vilar JMG. Synthetic cooperation in engineered yeast populations. Proc Natl Acad Sci U S A 2007; 104:1877-82. [PMID: 17267602 PMCID: PMC1794266 DOI: 10.1073/pnas.0610575104] [Citation(s) in RCA: 304] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2006] [Indexed: 11/18/2022] Open
Abstract
Cooperative interactions are key to diverse biological phenomena ranging from multicellularity to mutualism. Such diversity makes the ability to create and control cooperation desirable for potential applications in areas as varied as agriculture, pollutant treatment, and medicine. Here we show that persistent cooperation can be engineered by introducing a small set of genetic modifications into previously noninteracting cell populations. Specifically, we report the construction of a synthetic obligatory cooperative system, termed CoSMO (cooperation that is synthetic and mutually obligatory), which consists of a pair of nonmating yeast strains, each supplying an essential metabolite to the other strain. The behavior of the two strains in isolation, however, revealed unintended constraints that restrict cooperation, such as asymmetry in starvation tolerance and delays in nutrient release until near cell death. However, the joint system is shown mathematically and experimentally to be viable over a wide range of initial conditions, with oscillating population ratio settling to a value predicted by nutrient supply and consumption. Unexpectedly, even in the absence of explicitly engineered mechanisms to stabilize cooperation, the cooperative system can consistently develop increased ability to survive reductions in population density. Extending synthetic biology from the design of genetic circuits to the engineering of ecological interactions, CoSMO provides a quantitative system for linking processes at the cellular level to the collective behavior at the system level, as well as a genetically tractable system for studying the evolution of cooperation.
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Affiliation(s)
- Wenying Shou
- Computational Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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11
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Rébora K, Desmoucelles C, Borne F, Pinson B, Daignan-Fornier B. Yeast AMP pathway genes respond to adenine through regulated synthesis of a metabolic intermediate. Mol Cell Biol 2001; 21:7901-12. [PMID: 11689683 PMCID: PMC99957 DOI: 10.1128/mcb.21.23.7901-7912.2001] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Saccharomyces cerevisiae, AMP biosynthesis genes (ADE genes) are transcriptionally activated in the absence of extracellular purines by the Bas1p and Bas2p (Pho2p) transcription factors. We now show that expression of the ADE genes is low in mutant strains affected in the first seven steps of the pathway, while it is constitutively derepressed in mutant strains affected in later steps. Combined with epistasy studies, these results show that 5'-phosphoribosyl-4-succinocarboxamide-5-aminoimidazole (SAICAR), an intermediate metabolite of the pathway, is needed for optimal activation of the ADE genes. Two-hybrid studies establish that SAICAR is required to promote interaction between Bas1p and Bas2p in vivo, while in vitro experiments suggest that the effect of SAICAR on Bas1p-Bas2p interaction could be indirect. Importantly, feedback inhibition by ATP of Ade4p, catalyzing the first step of the pathway, appears to regulate SAICAR synthesis in response to adenine availability. Consistently, both ADE4 dominant mutations and overexpression of wild-type ADE4 lead to deregulation of ADE gene expression. We conclude that efficient transcription of yeast AMP biosynthesis genes requires interaction between Bas1p and Bas2p which is promoted in the presence of a metabolic intermediate whose synthesis is controlled by feedback inhibition of Ade4p acting as the purine nucleotide sensor within the cell.
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Affiliation(s)
- K Rébora
- Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, 33077 Bordeaux Cedex, France
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12
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Lecoq K, Konrad M, Daignan-Fornier B. Yeast GMP kinase mutants constitutively express AMP biosynthesis genes by phenocopying a hypoxanthine-guanine phosphoribosyltransferase defect. Genetics 2000; 156:953-61. [PMID: 11063676 PMCID: PMC1461337 DOI: 10.1093/genetics/156.3.953] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have characterized a new locus, BRA3, leading to deregulation of the yeast purine synthesis genes (ADE genes). We show that bra3 mutations are alleles of the GUK1 gene, which encodes GMP kinase. The bra3 mutants have a low GMP kinase activity, excrete purines in the medium, and show vegetative growth defects and resistance to purine base analogs. The bra3 locus also corresponds to the previously described pur5 locus. Several lines of evidence indicate that the decrease in GMP kinase activity in the bra3 mutants results in GMP accumulation and feedback inhibition of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), encoded by the HPT1 gene. First, guk1 and hpt1 mutants share several phenotypes, such as adenine derepression, purine excretion, and 8-azaguanine resistance. Second, overexpression of HPT1 allows suppression of the deregulated phenotype of the guk1 mutants. Third, we show that purified yeast HGPRT is inhibited by GMP in vitro. Finally, incorporation of hypoxanthine into nucleotides is similarly diminished in hpt1 and guk1 mutants in vivo. We conclude that the decrease in GMP kinase activity in the guk1 mutants results in deregulation of the ADE gene expression by phenocopying a defect in HGPRT. The possible occurrence of a similar phenomenon in humans is discussed.
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Affiliation(s)
- K Lecoq
- Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, 33077 Bordeaux Cedex, France
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13
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Eddy AA. Expulsion of uracil and thymine from the yeast Saccharomyces cerevisiae: contrasting responses to changes in the proton electrochemical gradient. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 1):219-229. [PMID: 9025296 DOI: 10.1099/00221287-143-1-219] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The outflow of uracil from the yeast Saccharomyces cerevisiae is known to be relatively fast in certain circumstances, to be retarded by proton conductors and to occur in strains lacking a uracil proton symport. In the present work, it was shown that uracil exit from washed yeast cells is an active process, creating a uracil gradient of the order of -80 mV relative to the surrounding medium. Glucose accelerated uracil exit, while retarding its entry. DNP or sodium azide each lowered the gradient to about -30 mV, simultaneously increasing the rate of uracil entry. They also lowered cellular ATP content. Manipulation of the external ionic conditions governing delta mu H+ at the plasma membrane had no detectable effect on uracil transport in yeast preparations thoroughly depleted of ATP. It was concluded that uracil exit is probably not driven by the proton gradient but may utilize ATP directly. It is known that thymine is not normally absorbed by yeast. However, thymine expulsion was here observed during deamination of the substrate 5-methylcytosine in the presence of glucose. In the absence of glucose, or following ATP depletion, thymine uptake from the medium only occurred when delta mu H+ was dissipated, either by DNP or azide, or by manipulation of the external ionic environment. The yeast expelled absorbed thymine when delta mu H+ was restored to the physiological range. The properties of the system corresponded to those of an H+/thymine antiport that is distinct from the mechanism expelling uracil.
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Affiliation(s)
- A A Eddy
- Department of Biochemistry and Applied Molecular Biology, University of Manchester Institute of Science and Technology, PO Box 88, Manchester M60 1QD, UK
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14
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Abstract
Compared with other purine salvage and nitrogen catabolism enzymatic activities, adenine deaminase (adenine aminohydrolase [AAH]; EC 3.5.4.2) activity in Saccharomyces cerevisiae is uniquely regulated. AAH specific activity is not induced by adenine and is reduced sevenfold when cells are cultivated in medium containing proline in place of ammonium as the sole nitrogen source. Exogenous adenine enters metabolic pathways primarily via the function of either AAH or adenine phosphoribosyltransferase (APRT; EC 2.4.2.7). Exogenous adenosine cannot normally be utilized as a purine source. Strains efficiently utilized adenosine or inosine when grown in pH 4.5 medium containing Triton X-100. A recessive mutation permitting utilization of adenosine or inosine in standard media was isolated. In both situations, growth of purine auxotrophs required either AAH or APRT activity. With medium containing either ammonium or proline as a nitrogen source, minimum doubling times of purine auxotrophs deficient in either APRT or AAH were measured. In proline-based medium, AAH and APRT permitted equal utilization of exogenous adenine. In ammonium-based medium, the absence of APRT increased the minimum doubling time by 50%. Similar experiments using sufficient exogenous histidine to feedback inhibit histidine biosynthesis failed to affect the growth rates of adenine auxotrophs blocked in AAH or APRT, indicating that the histidine-biosynthetic pathway does not play a significant role in adenine utilization. The gene that encodes AAH in S. cerevisiae was isolated by complementation using yeast strain XD1-1, which is deficient in AAH, APRT, and purine synthesis. A 1.36-kb EcoRI-SphI fragment was demonstrated to contain the structural gene for AAH by expressing this DNA in Escherichia coli under control of the trp promoter-operator. Northern (RNA) studies using the AAH-, APRT-, and CDC3-coding regions indicated that AAH regulation was not mediated at the level of transcription or mRNA degradation.
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Affiliation(s)
- M C Deeley
- Department of Genetics, University of Washington, Seattle 98195
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15
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Van den Bergh F, Vincent MF, Jaeken J, Van den Berghe G. Radiochemical assay of adenylosuccinase: demonstration of parallel loss of activity toward both adenylosuccinate and succinylaminoimidazole carboxamide ribotide in liver of patients with the enzyme defect. Anal Biochem 1991; 193:287-91. [PMID: 1872474 DOI: 10.1016/0003-2697(91)90023-m] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A radiochemical assay for adenylosuccinase, an enzyme which intervenes twice in the biosynthesis of adenine nucleotides, has been developed. The two substrates of the enzyme, succinylaminoimidazole carboxamide ribotide (SAICAR) and adenylosuccinate (S-AMP), were synthesized in radioactive form by incubating [2,3-14C]fumarate and, respectively, AICAR and AMP with partially purified adenylosuccinase from yeast. Enzyme activities were determined by measuring the release of labeled fumarate after its separation from the substrate by chromatography on polyethyleneimine thin-layer plates. The ratio of the activity of adenylosuccinase measured with SAICAR compared to that with S-AMP was about 1 in crude extracts of rat liver and muscle and around 0.5 in human liver. In rat and human liver, but not in rat muscle, 20 to 40% of both activities of adenylosuccinase were lost after freezing at -80 degrees C followed by thawing. In the liver of patients with adenylosuccinase deficiency, in whom the deficiency had hitherto been measured only with S-AMP, the activity of the enzyme toward S-AMP and SAICAR was found to be lost in parallel. This is in accordance with the finding that both SAICA-riboside and succinyladenosine accumulate in adenylosuccinase-deficient patients.
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Affiliation(s)
- F Van den Bergh
- Laboratory of Physiological Chemistry, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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Puttick A, Phillips M, Todd NK. Observations on 6-mercaptopurine activity in Saccharomyces cerevisiae. FEMS Microbiol Lett 1985. [DOI: 10.1111/j.1574-6968.1985.tb01636.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Woods RA, Roberts DG, Friedman T, Jolly D, Filpula D. Hypoxanthine: guanine phosphoribosyltransferase mutants in Saccharomyces cerevisiae. MOLECULAR & GENERAL GENETICS : MGG 1983; 191:407-12. [PMID: 6355764 DOI: 10.1007/bf00425755] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Yeast mutants lacking activity of the enzyme hypoxanthine:guanine phosphoribosyltransferase (H:G-PRT) have been isolated by selecting for resistance to 8-azaguanine in a strain carrying the wild type allele, ade4%, of the gene coding for amidophosphoribosyltransferase (PRPPAT), the first enzyme of de novo purine synthesis. The mutants excrete purines and are cross-resistant to 8-azaadenine. They are recessive and represent a single complementation group, designated hpt1. Ade4-su, a prototrophic allele of ade4 with reduced activity of PRPPAT, is epistatic to hpt1, suppressing purine excretion and resistance to azaadenine but not resistance to azaguanine. The genotype ade2hpt1 does not respond to hypoxanthine. Hpt1 complements and is not closely linked to the purine excreting mutants pur1 to pur5. Hpt1 and pur6, a regultory mutant of PRPPAT, are also unlinked but do not complement, suggesting a protein-protein interaction between H:G-PRT and PRPPAT. Mycophenolic acid (MPA), an inhibitor of de novo guanine nucleotide synthesis, inhibits the growth of hpt1 and hpt1+. Xanthine allows both genotypes to grow in the presence of MPA whereas guanine only allows growth of hpt1+. Activity of A-PRT, X-PRT and H:G-PRT is present in hpt+. Hpt1 lacks activity of H:G-PRT but has normal A-PRT and X-PRT.
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Stayton MM, Rudolph FB, Fromm HJ. Regulation, genetics, and properties of adenylosuccinate synthetase: a review. CURRENT TOPICS IN CELLULAR REGULATION 1983; 22:103-41. [PMID: 6347525 DOI: 10.1016/b978-0-12-152822-5.50008-7] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Levine RA, Taylor MW. Selection for purine regulatory mutants in an E. coli hypoxanthine phosphoribosyl transferase-guanine phosphoribosyl transferase double mutant. MOLECULAR & GENERAL GENETICS : MGG 1981; 181:313-8. [PMID: 6787390 DOI: 10.1007/bf00425604] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We have studied the relationship betwen purine salvage enzymes, 6-mercaptopurine resistance, and the purR phenotype in E. coli. Mutants resistant to 6-mercaptopurine were found to have defects in HPRT, the purR repressor, or in both. Analysis of these mutants led to the isolation of a hypoxanthine phosphoribosyl transferase-guanine phosphoribosyl transferase double mutant (hpt- gpt-) that is extremely sensitive to adenine. Two classes of adenine resistant mutants were isolated from this strain. The first class was deficient in APRT (apt-) while the second class represented purine regulatory mutants (purR-). There is thus selection for the purR phenotype in a hpt- gpt- background.
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Abstract
Four caffeine-resistant haploid isolates, two resistant to 50 mM caffeine and two resistant to 100 mM caffeine, were genetically analyzed. Complementation and tetrad analysis indicated that all four mutations are alleles of the same locus. All four isolates demonstrated incomplete dominance when hybridized to the wild-type strain and dominance of high to low resistance when hybridized to one another. Differences in caffeine resistance were found between wild-type grande cells and its petite derivative.
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Irwin M, Oates DC, Patterson D. Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism: isolation and characterization of a mutant deficient in the activity of phosphoribosylaminoimidazole synthetase. SOMATIC CELL GENETICS 1979; 5:203-16. [PMID: 483121 DOI: 10.1007/bf01539161] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A new purine-requiring mutant of Chinese hamster ovary cells (CHO-Kl) is described. This mutant, Ade-G, grows on aminoimidazole carboxamide, hypoxanthine, or adenine. It complements all eight of our other previously described Ade- mutants. Biochemical analysis of de novo purine synthesis in whole cells suggests that Ade-G is capable of the first four reactions of de novo purine biosynthesis and that it synthesizes and accumulates phosphoribosylformylglycinamidine (FGAM). Direct enzyme assay in cell-free extracts confirms that Ade-G is defective in phosphoribosylaminoimidazole synthetase activity and does not convert FGAM to phosphoribosylaminoimidazole (AIR), the next intermediate in the de novo biosynthetic pathway.
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Tu AS, Patterson D. Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism. VI. Enzymatic studies of two mutants unable to convert inosinic acid to adenylic acid. Biochem Genet 1977; 15:195-210. [PMID: 849250 DOI: 10.1007/bf00484561] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ade-H and ade-I are two auxotrophic mutants of Chinese hamster ovary (CHO-K1) cells which specifically require adenine as the purine source to grow. The enzymatic defects of these mutants were examined in cell-free extracts. It was found that ade-H did not have any detectable adenylosuccinate synthetase activity and ade-I was defective in the adenylosuccinate lyase enzyme. The relevance of adenine-requiring mutants to the study of the regulation of purine metabolism in mammalian cells is discussed.
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Henderson JF, Burridge PW, Woods RA. Altered synthesis and catabolism of purine nucleotides in regulatory mutants of Saccharomyces cerevisiae. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1977; 76A:59-63. [PMID: 324248 DOI: 10.1007/978-1-4613-4223-6_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Benson CE, Gots JS. Occurrence of a regulatory deficiency in purine biosynthesis among pur A mutants of Salmonella typhimurium. MOLECULAR & GENERAL GENETICS : MGG 1976; 145:31-6. [PMID: 775307 DOI: 10.1007/bf00331554] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A defect in the repression of the de novo purine biosynthetic enzymes was detected among purA mutants of Salmonella typhimurium. We suggest that the defect is caused by an altered purine regulation gene (purR) which affects the response level of at least five of the de novo enzymes to repression by excess adenine. Thus the unlinked genes controlling these enzymes constitute a regulation controlled wholly or in part by a purR gene product. The regulation of the guanine operon is regulated by some other mechanism independent of purR.
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Patterson D. Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism III. Isolation and characterization of a mutant unable to convert IMP to AMP. SOMATIC CELL GENETICS 1976; 2:41-53. [PMID: 1028159 DOI: 10.1007/bf01539241] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The isolation and characterization of a new mutant of Chinese ovary cells (CHO-K1) is described. This mutant, Ade-H, has the following properties: (1) it forms a new genetic complementation group; (2) it specifically requires adenine for growth and will not grow on aminoimidazole carboxamide (AIC) or hypoxanthine; (3) it accumulates IMP; (4) it cannot synthesize adenine nucleotides; (5) its phenotype can be mimicked by treatment of CHO-K1 (the wild type parental strain) with hadacidin, an inhibitor of adenylosuccinate synthetase (E.C.6.3.4.4). Thus, the site of the defect in this mutant is presumed to involve the step in adenylate biosynthesis catalyzed by this enzyme. The usefulness of Ade-H for the study of regulation of purine biosynthesis in mammalian cells is discussed.
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Pendyala L, Wellman AM. Effect of histidine on purine nucleotide synthesis and utilization in Neurospora crassa. J Bacteriol 1975; 124:78-85. [PMID: 126229 PMCID: PMC235867 DOI: 10.1128/jb.124.1.78-85.1975] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Histidine affects de novo purine nucleotide synthesis and purine nucleotide pool utilization in Neurospora crassa. The former effect was assessed qualitatively by the presence or absence of purple pigment production in ad3B and ad3A mutants. Tryptophan also affected the de novo purine nucleotide synthesis. The effect of histidine on purine nucleotide pool utilization resulted in stimulated germination of ad8 and ad4 mutant conidia in adenine-deficient medium. Increased germination was correlated with increased net levels of nucleic acids in these strains. Possible mechanisms for the dual action of histidine are discussed.
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Pickering WR, Woods RA. Genetics of resistance to 4-aminopyrazolo-(3,4-d)-pyrimidine in Saccharomyces cerevisiae. MOLECULAR & GENERAL GENETICS : MGG 1973; 122:231-42. [PMID: 4577899 DOI: 10.1007/bf00278599] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Lomax CA, Woods RA. A complex genetic locus controlling purine nucleotide biosynthesis in yeast. MOLECULAR & GENERAL GENETICS : MGG 1973; 120:139-49. [PMID: 4568528 DOI: 10.1007/bf00267242] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Gross TS, Woods RA. Identification of mutants defective in the first and second steps of de novo purine synthesis in Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA 1971; 247:13-21. [PMID: 4334353 DOI: 10.1016/0005-2787(71)90802-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Abstract
Six mutants, allelic to ade3, were isolated after mutagenic treatment of a prototrophic strain of yeast. All six grow on medium supplemented with adenine alone and four respond to histidine. Supplementation with adenine plus histidine or methionine inhibits growth, but a mixture of these three is stimulatory. Heteroallelic diploids formed by the new mutants with the standard ade3 can resemble either parent or show an intermediate phenotype. The new mutants, unlike standard ade3, are not fully epistatic to ade2. The activities of three enzymes concerned in tetrahydrofolate metabolism have been assayed in the new and standard ade3 mutants and wild type. The only difference detected between the new and standard ade3 was in the levels of 10-formyltetrahydrofolate synthetase. Activity in the new mutants ranged from 36 to 109% of wild type compared with 10 to 12% in the standard ade3. Possible mechanisms to account for the varied phenotypes at the ade3 locus are discussed.
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Lomax CA, Woods RA. Prototrophic regulatory mutants of adenylosuccinate synthetase in yeast. NATURE: NEW BIOLOGY 1971; 229:116. [PMID: 4934156 DOI: 10.1038/newbio229116a0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Dorfman BZ, Goldfinger BA, Berger M, Goldstein S. Partial reversion in yeast: genetic evidence for a new type of bifunctional protein. Science 1970; 168:1482-4. [PMID: 5445943 DOI: 10.1126/science.168.3938.1482] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Two kinds of phenotypic expression in purine biosynthesis result from recessive mutation to adel2 in baker's yeast. The mutants are adenine-specific, blocked in the conversion of inosine 5'-phosphate to adenylosuccinic acid; their response to inhibition of pathway activity by adenine is considerably reduced. Allelic partial reversions can restore prototrophy without correcting the regulatory defect imparted by the primary mutation. The separation of the two properties of the locus by allelic mutation supports the hypothesis that the locus specifies a protein of two independent functions, enzymatic and regulatory.
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