The impact of oxygen on metabolic evolution: a chemoinformatic investigation

A new preparation method of covalent annular nanodiscs based on MTGase

The preservation of the native conformation and functionality of membrane proteins has posed considerable challenges. While detergents and liposome reconstitution have been traditional approaches, nanodiscs (NDs) offer a promising solution by embedding membrane proteins in phospholipids encircled by an amphipathic helical protein MSP belt. Nevertheless, a drawback of commonly used NDs is their limited homogeneity and stability. In this study, we present a novel approach to construct covalent annular nanodiscs (cNDs) by leveraging microbial transglutaminase (MTGase) to catalyze isopeptide bond formation between the side chains of terminal amino acids, specifically Lysine (K) and Glutamine (Q). This methodology significantly enhances the homogeneity and stability of NDs. Characterization of cNDs and the assembly of membrane proteins within them validate the successful reconstitution of membrane proteins with improved homogeneity and stability. Our findings suggest that cNDs represent a more suitable tool for investigating interactions between membrane proteins and lipids, as well as for analyzing membrane protein structures.

Physicochemical Foundations of Life that Direct Evolution: Chance and Natural Selection are not Evolutionary Driving Forces

The current framework of evolutionary theory postulates that evolution relies on random mutations generating a diversity of phenotypes on which natural selection acts. This framework was established using a top-down approach as it originated from Darwinism, which is based on observations made of complex multicellular organisms and, then, modified to fit a DNA-centric view. In this article, it is argued that based on a bottom-up approach starting from the physicochemical properties of nucleic and amino acid polymers, we should reject the facts that (i) natural selection plays a dominant role in evolution and (ii) the probability of mutations is independent of the generated phenotype. It is shown that the adaptation of a phenotype to an environment does not correspond to organism fitness, but rather corresponds to maintaining the genome stability and integrity. In a stable environment, the phenotype maintains the stability of its originating genome and both (genome and phenotype) are reproduced identically. In an unstable environment (i.e., corresponding to variations in physicochemical parameters above a physiological range), the phenotype no longer maintains the stability of its originating genome, but instead influences its variations. Indeed, environment- and cellular-dependent physicochemical parameters define the probability of mutations in terms of frequency, nature, and location in a genome. Evolution is non-deterministic because it relies on probabilistic physicochemical rules, and evolution is driven by a bidirectional interplay between genome and phenotype in which the phenotype ensures the stability of its originating genome in a cellular and environmental physicochemical parameter-depending manner.

A Systematic Cheminformatics Analysis of Functional Groups Occurring in Natural Products

The two most striking features that discriminate natural products from synthetic molecules are their characteristic scaffolds and unique functional groups (FGs). In this study we systematically investigate the distribution of FGs in natural products from a cheminformatics perspective by comparing FG frequencies in natural products with those found in average synthetic molecules. We thereby aim for the identification of FGs that are characteristic for molecules produced by living organisms. In our analysis we also include information about the natural origins of the structures investigated, allowing us to link the occurrence of specific FGs to the individual producing species. Our findings have the potential for being applied in a medicinal chemistry context concerning the synthesis of natural product-like libraries and natural product-inspired fragment collections. The results may be used also to support compound derivatization strategies and the design of "non-natural" natural products.

A power law distribution of metabolite abundance levels in mice regardless of the time and spatial scale of analysis

Biomolecule abundance levels change with the environment and enable a living system to adapt to the new conditions. Although, the living system maintains at least some characteristics, e.g. homeostasis. One of the characteristics maintained by a living system is a power law distribution of biomolecule abundance levels. Previous studies have pointed to a universal characteristic of biochemical reaction networks, with data obtained from lysates of multiple cells. As a result, the spatial scale of the data related to the power law distribution of biomolecule abundance levels is not clear. In this study, we researched the scaling law of metabolites in mouse tissue with a spatial scale of quantification that was changed stepwise between a whole-tissue section and a single-point analysis (25 μm). As a result, metabolites in mouse tissues were found to follow the power law distribution independently of the spatial scale of analysis. Additionally, we tested the temporal changes by comparing data from younger and older mice. Both followed similar power law distributions, indicating that metabolite composition is not diversified by aging to disrupt the power law distribution. The power law distribution of metabolite abundance is thus a robust characteristic of a living system regardless of time and space.

Cell-Autonomous Metabolic Reprogramming in Hypoxia

Molecular oxygen (O₂) is a universal electron acceptor that enables ATP synthesis through mitochondrial respiration in all metazoans. Consequently, hypoxia (low O₂) has arisen as an organizing principle for cellular evolution, metabolism, and (patho)biology, eliciting a remarkable panoply of metabolic adaptations that trigger transcriptional, translational, post-translational, and epigenetic responses to determine cellular fitness. In this review we summarize current and emerging cell-autonomous molecular mechanisms that induce hypoxic metabolic reprogramming in health and disease.

One step beyond a ribosome: The ancient anaerobic core

Life arose in a world without oxygen and the first organisms were anaerobes. Here we investigate the gene repertoire of the prokaryote common ancestor, estimating which genes it contained and to which lineages of modern prokaryotes it was most similar in terms of gene content. Using a phylogenetic approach we found that among trees for all 8779 protein families shared between 134 archaea and 1847 bacterial genomes, only 1045 have sequences from at least two bacterial and two archaeal groups and retain the ancestral archaeal–bacterial split. Among those, the genes shared by anaerobes were identified as candidate genes for the prokaryote common ancestor, which lived in anaerobic environments. We find that these anaerobic prokaryote common ancestor genes are today most frequently distributed among methanogens and clostridia, strict anaerobes that live from low free energy changes near the thermodynamic limit of life. The anaerobic families encompass genes for bifunctional acetyl-CoA-synthase/CO-dehydrogenase, heterodisulfide reductase subunits C and A, ferredoxins, and several subunits of the Mrp-antiporter/hydrogenase family, in addition to numerous S-adenosyl methionine (SAM) dependent methyltransferases. The data indicate a major role for methyl groups in the metabolism of the prokaryote common ancestor. The data furthermore indicate that the prokaryote ancestor possessed a rotor stator ATP synthase, but lacked cytochromes and quinones as well as identifiable redox-dependent ion pumping complexes. The prokaryote ancestor did possess, however, an Mrp-type H⁺/Na⁺ antiporter complex, capable of transducing geochemical pH gradients into biologically more stable Na⁺-gradients. The findings implicate a hydrothermal, autotrophic, and methyl-dependent origin of life. This article is part of a Special Issue entitled ‘EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2–6, 2016’, edited by Prof. Paolo Bernardi.

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Life arose without oxygen, the universal ancestor (Luca) was an anaerobe.

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We used phylogenetic and physiological criteria to identify genes present in Luca.

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An ancient core of 65 metabolic genes shed light on Luca's anaerobic lifestyle.

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Ancient core genes are most widespread among modern methanogens and clostridia.

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The data implicate a major role for methyl groups in Luca's anaerobic metabolism.

Shared Genetic Signals of Hypoxia Adaptation in Drosophila and in High-Altitude Human Populations

The ability to withstand low oxygen (hypoxia tolerance) is a polygenic and mechanistically conserved trait that has important implications for both human health and evolution. However, little is known about the diversity of genetic mechanisms involved in hypoxia adaptation in evolving populations. We used experimental evolution and whole-genome sequencing in Drosophila melanogaster to investigate the role of natural variation in adaptation to hypoxia. Using a generalized linear mixed model we identified significant allele frequency differences between three independently evolved hypoxia-tolerant populations and normoxic control populations for approximately 3,800 single nucleotide polymorphisms. Around 50% of these variants are clustered in 66 distinct genomic regions. These regions contain genes that are differentially expressed between hypoxia-tolerant and normoxic populations and several of the differentially expressed genes are associated with metabolic processes. Additional genes associated with respiratory and open tracheal system development also show evidence of directional selection. RNAi-mediated knockdown of several candidate genes’ expression significantly enhanced survival in severe hypoxia. Using genomewide single nucleotide polymorphism data from four high-altitude human populations—Sherpas, Tibetans, Ethiopians, and Andeans, we found that several human orthologs of the genes under selection in flies are also likely under positive selection in all four high-altitude human populations. Thus, our results indicate that selection for hypoxia tolerance can act on standing genetic variation in similar genes and pathways present in organisms diverged by hundreds of millions of years.

Computing the origin and evolution of the ribosome from its structure - Uncovering processes of macromolecular accretion benefiting synthetic biology

Accretion occurs pervasively in nature at widely different timeframes. The process also manifests in the evolution of macromolecules. Here we review recent computational and structural biology studies of evolutionary accretion that make use of the ideographic (historical, retrodictive) and nomothetic (universal, predictive) scientific frameworks. Computational studies uncover explicit timelines of accretion of structural parts in molecular repertoires and molecules. Phylogenetic trees of protein structural domains and proteomes and their molecular functions were built from a genomic census of millions of encoded proteins and associated terminal Gene Ontology terms. Trees reveal a ‘metabolic-first’ origin of proteins, the late development of translation, and a patchwork distribution of proteins in biological networks mediated by molecular recruitment. Similarly, the natural history of ancient RNA molecules inferred from trees of molecular substructures built from a census of molecular features shows patchwork-like accretion patterns. Ideographic analyses of ribosomal history uncover the early appearance of structures supporting mRNA decoding and tRNA translocation, the coevolution of ribosomal proteins and RNA, and a first evolutionary transition that brings ribosomal subunits together into a processive protein biosynthetic complex. Nomothetic structural biology studies of tertiary interactions and ancient insertions in rRNA complement these findings, once concentric layering assumptions are removed. Patterns of coaxial helical stacking reveal a frustrated dynamics of outward and inward ribosomal growth possibly mediated by structural grafting. The early rise of the ribosomal ‘turnstile’ suggests an evolutionary transition in natural biological computation. Results make explicit the need to understand processes of molecular growth and information transfer of macromolecules.

The proportion of genes in a functional category is linked to mass-specific metabolic rate and lifespan

Metabolic rate and lifespan are important biological parameters that are studied in a wide range of research fields. They are known to correlate with body mass, but their association with gene (protein) functions is poorly understood. In this study, we collected data on the metabolic rate and lifespan of various organisms and investigated the relationship of these parameters with their genomes. We showed that the proportion of genes in a functional category, but not genome size, was correlated with mass-specific metabolic rate and maximal lifespan. In particular, the proportion of genes in oxic reactions (which occur in the presence of oxygen) was significantly associated with these two biological parameters. Additionally, we found that temperature, taxonomy, and mode-of-life traits had little effect on the observed associations. Our findings emphasize the importance of considering the biological functions of genes when investigating the relationships between genome, metabolic rate, and lifespan. Moreover, this provides further insights into these relationships, and may be useful for estimating metabolic rate and lifespan in individuals and the ecosystem using a combination of body mass measurements and genomic data.

Nonenzymatic Reactions above Phospholipid Surfaces of Biological Membranes: Reactivity of Phospholipids and Their Oxidation Derivatives

Phospholipids play multiple and essential roles in cells, as components of biological membranes. Although phospholipid bilayers provide the supporting matrix and surface for many enzymatic reactions, their inherent reactivity and possible catalytic role have not been highlighted. As other biomolecules, phospholipids are frequent targets of nonenzymatic modifications by reactive substances including oxidants and glycating agents which conduct to the formation of advanced lipoxidation end products (ALEs) and advanced glycation end products (AGEs). There are some theoretical studies about the mechanisms of reactions related to these processes on phosphatidylethanolamine surfaces, which hypothesize that cell membrane phospholipids surface environment could enhance some reactions through a catalyst effect. On the other hand, the phospholipid bilayers are susceptible to oxidative damage by oxidant agents as reactive oxygen species (ROS). Molecular dynamics simulations performed on phospholipid bilayers models, which include modified phospholipids by these reactions and subsequent reactions that conduct to formation of ALEs and AGEs, have revealed changes in the molecular interactions and biophysical properties of these bilayers as consequence of these reactions. Then, more studies are desirable which could correlate the biophysics of modified phospholipids with metabolism in processes such as aging and diseases such as diabetes, atherosclerosis, and Alzheimer's disease.

PhIN: A Protein Pharmacology Interaction Network Database

Network pharmacology is a new and hot concept in drug discovery for its ability to investigate the complexity of polypharmacology, and becomes more and more important in drug development. Here we report a protein pharmacology interaction network database (PhIN), aiming to assist multitarget drug discovery by providing comprehensive and flexible network pharmacology analysis. Overall, PhIN contains 1,126,060 target–target interaction pairs in terms of shared compounds and 3,428,020 pairs in terms of shared scaffolds, which involve 12,419,700 activity data, 9,414 targets, 314 viral targets, 652 pathways, 1,359,400 compounds, and 309,556 scaffolds. Using PhIN, users can obtain interacting target networks within or across human pathways, between human and virus, by defining the number of shared compounds or scaffolds under an activity cutoff. We expect PhIN to be a useful tool for multitarget drug development. PhIN is freely available at http://cadd.pharmacy.nankai.edu.cn/phin/.

Chemical reactivity drives spatiotemporal organisation of bacterial metabolism

In this review, we examine how bacterial metabolism is shaped by chemical constraints acting on the material and dynamic layout of enzymatic networks and beyond. These are moulded not only for optimisation of given metabolic objectives (e.g. synthesis of a particular amino acid or nucleotide) but also for curbing the detrimental reactivity of chemical intermediates. Besides substrate channelling, toxicity is avoided by barriers to free diffusion (i.e. compartments) that separate otherwise incompatible reactions, along with ways for distinguishing damaging vs. harmless molecules. On the other hand, enzymes age and their operating lifetime must be tuned to upstream and downstream reactions. This time dependence of metabolic pathways creates time-linked information, learning and memory. These features suggest that the physical structure of existing biosystems, from operon assemblies to multicellular development may ultimately stem from the need to restrain chemical damage and limit the waste inherent to basic metabolic functions. This provides a new twist of our comprehension of fundamental biological processes in live systems as well as practical take-home lessons for the forward DNA-based engineering of novel biological objects.

A calibrated chronology of biochemistry reveals a stem line of descent responsible for planetary biodiversity

Time-calibrated phylogenomic trees of protein domain structure produce powerful chronologies describing the evolution of biochemistry and life. These timetrees are built from a genomic census of millions of encoded proteins using models of nested accumulation of molecules in evolving proteomes. Here we show that a primordial stem line of descent, a propagating series of pluripotent cellular entities, populates the deeper branches of the timetrees. The stem line produced for the first time cellular grades ~2.9 billion years (Gy)-ago, which slowly turned into lineages of superkingdom Archaea. Prompted by the rise of planetary oxygen and aerobic metabolism, the stem line also produced bacterial and eukaryal lineages. Superkingdom-specific domain repertoires emerged ~2.1 Gy-ago delimiting fully diversified Bacteria. Repertoires specific to Eukarya and Archaea appeared 300 millions years later. Results reconcile reductive evolutionary processes leading to the early emergence of Archaea to superkingdom-specific innovations compatible with a tree of life rooted in Bacteria.

Limited influence of oxygen on the evolution of chemical diversity in metabolic networks

Oxygen is thought to promote species and biomolecule diversity. Previous studies have suggested that oxygen expands metabolic networks by acquiring metabolites with different chemical properties (higher hydrophobicity, for example). However, such conclusions are typically based on biased evaluation, and are therefore non-conclusive. Thus, we re-investigated the effect of oxygen on metabolic evolution using a phylogenetic comparative method and metadata analysis to reduce the bias as much as possible. Notably, we found no difference in metabolic network expansion between aerobes and anaerobes when evaluating phylogenetic relationships. Furthermore, we showed that previous studies have overestimated or underestimated the degrees of differences in the chemical properties (e.g., hydrophobicity) between oxic and anoxic metabolites in metabolic networks of unicellular organisms; however, such overestimation was not observed when considering the metabolic networks of multicellular organisms. These findings indicate that the contribution of oxygen to increased chemical diversity in metabolic networks is lower than previously thought; rather, phylogenetic signals and cell-cell communication result in increased chemical diversity. However, this conclusion does not contradict the effect of oxygen on metabolic evolution; instead, it provides a deeper understanding of how oxygen contributes to metabolic evolution despite several limitations in data analysis methods.

Structural phylogenomics reveals gradual evolutionary replacement of abiotic chemistries by protein enzymes in purine metabolism

The origin of metabolism has been linked to abiotic chemistries that existed in our planet at the beginning of life. While plausible chemical pathways have been proposed, including the synthesis of nucleobases, ribose and ribonucleotides, the cooption of these reactions by modern enzymes remains shrouded in mystery. Here we study the emergence of purine metabolism. The ages of protein domains derived from a census of fold family structure in hundreds of genomes were mapped onto enzymes in metabolic diagrams. We find that the origin of the nucleotide interconversion pathway benefited most parsimoniously from the prebiotic formation of adenine nucleosides. In turn, pathways of nucleotide biosynthesis, catabolism and salvage originated ∼300 million years later by concerted enzymatic recruitments and gradual replacement of abiotic chemistries. Remarkably, this process led to the emergence of the fully enzymatic biosynthetic pathway ∼3 billion years ago, concurrently with the appearance of a functional ribosome. The simultaneous appearance of purine biosynthesis and the ribosome probably fulfilled the expanding matter-energy and processing needs of genomic information.

Oxidative DNA damage is important to the evolution of antibiotic resistance: evidence of mutation bias and its medicinal implications

Several (1) studies have revealed that the reactive oxygen species (ROS) induced by antibacterial stimulation accelerates the evolution of antibiotic resistance, which uncovered new links between oxygen rise and evolution and inspired new strategies to prevent antibiotic resistance. Considering many other mechanisms cause DNA mutations aside from ROS damage, evaluating the significance of oxidative DNA damage in the development of antibiotic resistance is of great interest. In this study, we examined the ratio of G:C > T:A transversion to G:C > A:T transition in drug-resistant Escherichia coli and Mycobacterium tuberculosis and found that it is significantly higher than the background values. This finding strongly suggests that ROS damage plays a critical role in the development of antibacterial resistance. Considering the long-term co-evolution between host organisms and pathogenic bacteria, we speculate that the hosts may have evolved strategies for combating antibiotic resistance by controlling DNA damage in bacteria. Analysis of the global transcriptional profiles of Staphylococcus aureus treated with berberine (derived from Berberis, a traditional antibacterial medicine) revealed that the transcription of DNA repair enzymes was markedly upregulated, whereas the antioxidant enzymes were significantly downregulated. Thus, we propose that consolidating the DNA repair systems of bacteria may be a viable strategy for preventing antibiotic resistance. (1)These authors contributed equally to this work.

Current understanding of the formation and adaptation of metabolic systems based on network theory

Formation and adaptation of metabolic networks has been a long-standing question in biology. With recent developments in biotechnology and bioinformatics, the understanding of metabolism is progressively becoming clearer from a network perspective. This review introduces the comprehensive metabolic world that has been revealed by a wide range of data analyses and theoretical studies; in particular, it illustrates the role of evolutionary events, such as gene duplication and horizontal gene transfer, and environmental factors, such as nutrient availability and growth conditions, in evolution of the metabolic network. Furthermore, the mathematical models for the formation and adaptation of metabolic networks have also been described, according to the current understanding from a perspective of metabolic networks. These recent findings are helpful in not only understanding the formation of metabolic networks and their adaptation, but also metabolic engineering.