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The FEBS Journal May 2008Peptides function as chemical signals between cells of multicellular organisms via specific receptors on target cells. Many hormones, neuromodulators and growth factors... (Review)
Review
Peptides function as chemical signals between cells of multicellular organisms via specific receptors on target cells. Many hormones, neuromodulators and growth factors are peptides. Peptide hormones and other biologically active peptides are synthesized as higher molecular weight precursor proteins (pro-hormones), which must undergo post-translational modification to yield the bioactive peptide(s). In many instances, more than one biologically active peptide is generated from one and the same precursor. In most cases, these precursors are biologically inert and their existence is confined to the membrane-enclosed subcellular compartments where processing of the pro-hormones takes place. A class of growth factors that derive from membrane-anchored precursors which themselves are biologically active constitute an exception to this model. The list of the membrane-anchored biologically active precursors has been the subject of specialized reviews. The present review focuses on precursors other than membrane-anchored precursors, which were found to be biologically active and which often display different biological activities, and may mediate their effects via receptors independent from those of their generated peptides.
Topics: Animals; Humans; Peptide Fragments; Peptide Hormones; Protein Precursors
PubMed: 18384380
DOI: 10.1111/j.1742-4658.2008.06366.x -
Cellulose (London, England) 2021Polyacrylonitrile (PAN)-based carbon precursor is a well-established and researched material for electrodes in energy storage applications due to its good physical... (Review)
Review
Polyacrylonitrile (PAN)-based carbon precursor is a well-established and researched material for electrodes in energy storage applications due to its good physical properties and excellent electrochemical performance. However, in the fight of preserving the environment and pioneering renewable energy sources, environmentally sustainable carbon precursors with superior electrochemical performance are needed. Therefore, bio-based materials are excellent candidates to replace PAN as a carbon precursor. Depending on the design requirement (e.g. carbon morphology, doping level, specific surface area, pore size and volume, and electrochemical performance), the appropriate selection of carbon precursors can be made from a variety of biomass and biowaste materials. This review provides a summary and discussion on the preparation and characterization of the emerging and recent bio-based carbon precursors that can be used as electrodes in energy storage applications. The review is outlined based on the morphology of nanostructures and the precursor's type. Furthermore, the review discusses and summarizes the excellent electrochemical performance of these recent carbon precursors in storage energy applications. Finally, a summary and outlook are also given. All this together portrays the promising role of bio-based carbon electrodes in energy storage applications.
PubMed: 33897123
DOI: 10.1007/s10570-021-03881-z -
RNA (New York, N.Y.) Apr 2007Most of the vertebrate genome is transcribed into RNA. Transcribed regions contain hundreds of thousands of potential duplex structures that could serve as substrates... (Review)
Review
Most of the vertebrate genome is transcribed into RNA. Transcribed regions contain hundreds of thousands of potential duplex structures that could serve as substrates for RNAse III enzymes of microRNA (miRNA) maturation pathways. Yet, only a minority of these potential precursors make their way to the cytoplasm to form mature miRNAs. We question here what specific structural features make an RNA stem-loop structure an adequate primary or precursor miRNA. We address this question by comparing known pre-miRNAs to other predicted noncoding transcripts obtained from comparative genomics scans, using the structure comparison program RNAforester. By analyzing a classification tree of 1200 such RNA structures, we observe that pre-miRNAs cluster distinctly from other duplex structures of apparently similar size and free energy. The most distinctive features of nonprecursor duplexes are increased lengths and numbers of bulges and internal loops when compared to real miRNA precursors. Thanks to these characteristics, secondary structure comparison can predict the miRNA precursor status of a candidate stem-loop with a surprising accuracy. Furthermore, predicted noncoding transcripts tend to depart from miRNA precursor characteristics more strongly than randomly occurring duplex structures in genomic DNA. This result suggests that many noncoding RNAs may be under selection to dodge the RNAi pathway.
Topics: Animals; Base Sequence; Humans; MicroRNAs; Models, Chemical; Models, Genetic; Models, Structural; Nucleic Acid Conformation; RNA; RNA Interference; RNA Precursors; Ribonuclease III
PubMed: 17299129
DOI: 10.1261/rna.366507 -
Kidney International. Supplement May 2003Hyperhomocysteinemia is a risk factor for cardiovascular disease in the general population. In chronic renal failure (CRF), plasma homocysteine levels rise when the... (Review)
Review
Hyperhomocysteinemia is a risk factor for cardiovascular disease in the general population. In chronic renal failure (CRF), plasma homocysteine levels rise when the glomerular filtration rate (GFR) is reduced 50%, and in uremia the majority of patients are hyperhomocysteinemic. The purpose of this study was to review possible mechanisms of homocysteine toxicity. Homocysteine, a sulfur amino acid found in blood in micromolar concentrations, can have toxic effects through a handful of general possible mechanisms. These mechanisms include oxidative stress (through the production of reactive oxygen species), binding to nitric oxide, production of homocysteinylated/acylated proteins, and accumulation of its precursor, S-adenosyl-homocysteine, a potent inhibitor of transmethylation reactions. Methyltransferase inhibition actually occurs in CRF and in uremia, and can have several functional consequences.
Topics: Homocysteine; Humans; Hyperhomocysteinemia; Toxins, Biological; Uremia
PubMed: 12694330
DOI: 10.1046/j.1523-1755.63.s84.33.x -
Experimental and Therapeutic Medicine Feb 2020-Allyl-L-cysteine sulfoxide (ACSO) is an odour precursor in garlic bulbs. One plausible pathway for the biosynthesis of ACSO involves -2-carboxypropyl glutathione... (Review)
Review
-Allyl-L-cysteine sulfoxide (ACSO) is an odour precursor in garlic bulbs. One plausible pathway for the biosynthesis of ACSO involves -2-carboxypropyl glutathione produced from glutathione and methacrylic acid via valine or from γ-glutamyl cysteine. The elimination of glycine and glutamic acid from -2-carboxypropyl glutathione produces -2-carboxypropyl cysteine, which is converted to -allyl cysteine by decarboxylation and oxidation. -Allyl cysteine is also biosynthesized via the elimination of glutamic acid from γ-glutamyl -allyl cysteine by γ-glutamyl transpeptidase. The sulfur oxidation of -allyl cysteine by flavin-containing monooxygenase forms ACSO. When cells are damaged by slicing or grating, ACSO in the cytoplasm or cytoplasmic vesicle is immediately converted to allylsulfenic acid, pyruvic acid, and ammonia by alliinase (C-S lyase), which is located in the vacuoles of vascular bundle sheath cells. Two molecules of allylsulfenic acid form diallyl thiosulfinate (allicin), which exhibits potent antimicrobial activity. Allicin eventually yields garlic odour compounds, such as diallyl disulfide (DADS) and diallyl trisulfide (DATS). Although these sulfides are known to exert various physiological functions, their strong odour limits their use in foods. On the other hand, ACSO is water-soluble and odourless and enhances sweet, salty, and umami tastes, characteristics of which are desirable for food additives. Upon consumption, ACSO is primarily absorbed from the small intestine in the intact form, but is also partly decomposed to allylsulfenic acid, pyruvic acid and ammonia. Allylsulfenic acid is then further converted to DADS and diallyl monosulfide (DAS). ACSO has numerous functions, such as the prevention of diabetes, myocardial ischaemia, hepatic injury, platelet aggregation and blood ethanol elevation. Although some of these effects may be attributed to its metabolites, ACSO itself contributes to many of these physiological functions.
PubMed: 32010334
DOI: 10.3892/etm.2019.8385 -
Biochemistry Feb 2020Hedgehog proteins, a family of vital cell signaling factors, are expressed in precursor form, which requires specialized autoprocessing, called cholesterolysis, for full...
Hedgehog proteins, a family of vital cell signaling factors, are expressed in precursor form, which requires specialized autoprocessing, called cholesterolysis, for full biological activity. Cholesterolysis occurs through the action of the precursor's C-terminal enzymatic domain, HhC. In this work, we describe HhC activator compounds (HACs), a novel class of noncovalent modulators that induce autoprocessing infidelity, diminishing native cholesterolysis in favor of precursor autoproteolysis, an otherwise minor and apparently nonphysiological side reaction. HAC-induced autoproteolysis generates hedgehog protein that is cholesterol free and hence signaling deficient. The most effective HAC has an AC of 9 μM, accelerates HhC autoproteolytic activity by 225-fold, and functions in the presence and absence of cholesterol, the native substrate. HACs join a rare class of "antagonists" that suppress native enzymatic activity by subverting mechanistic fidelity.
Topics: Catalysis; Cholesterol; Drosophila Proteins; Genetic Variation; Hedgehog Proteins; Proteolysis
PubMed: 32013401
DOI: 10.1021/acs.biochem.0c00013 -
Neurogenesis (Austin, Tex.) 2014During early stages of development of the vertebrate central nervous system, neural precursors divide symmetrically to produce new precursors, thereby expanding the...
During early stages of development of the vertebrate central nervous system, neural precursors divide symmetrically to produce new precursors, thereby expanding the precursor population. During middle stages of neural development, precursors switch to an asymmetric division pattern whereby each mitosis produces one new precursor and one cell that differentiates as a neuron or glial cell. At late stages of development, most precursors stop dividing and terminally differentiate. Par complex proteins are associated with the apical membrane of neural precursors and promote precursor self-renewal. How Par proteins are down regulated to bring precursor self-renewal to an end has not been known. Our investigations of zebrafish neural development revealed that the microRNA miR-219 negatively regulates apical Par proteins, thereby promoting cessation of neural precursor division and driving terminal differentiation.
PubMed: 27502270
DOI: 10.4161/23262133.2014.976018 -
Journal of Virology Aug 1976Three intermediates in adenovirus assembly have been defined; nuclear intermediates, young virions, and mature virions. The nuclear intermediates are fragile and...
Three intermediates in adenovirus assembly have been defined; nuclear intermediates, young virions, and mature virions. The nuclear intermediates are fragile and heterogenous in size (550S-670S) and withstand separation on ficoll gradients but fall apart upon CsCl gradient centrifugation unless prefixed with glutaraldehyde. They contain both capsid and core structures, and the core structures are preferentially released during purification in CsCl. The precursor polypeptides pVI and pVII are present in the intermediates without any corresponding mature polypeptide. The young virions (Ishibashi and Maizel, 1974) are stable and preferentially confined to the nuclei after cell fractionation. They contain both uncleaved precursor polypeptides and their cleavage products. The mature virions accumulate in the cytoplasm during cell fractionation and contain the final mature polypeptides. Pulse-chase labeling kinetics, focusing on the precursor polypeptides, suggest that these three classes participate in assembly of adenovirus. Tryptic peptide maps establish that polypeptide pVI is the precursor of polypeptide VI, but only a small fraction of polypeptide 26K can in vivo account for polypeptide VIII.
Topics: Adenoviridae; Cell Line; Centrifugation, Density Gradient; Peptides; Protein Precursors; Viral Proteins; Virus Replication
PubMed: 957481
DOI: 10.1128/JVI.19.2.533-547.1976 -
Biochimica Et Biophysica Acta Jan 1989Most mitochondrial proteins are synthesized as precursor proteins on cytosolic polysomes and are subsequently imported into mitochondria. Many precursors carry... (Review)
Review
Most mitochondrial proteins are synthesized as precursor proteins on cytosolic polysomes and are subsequently imported into mitochondria. Many precursors carry amino-terminal presequences which contain information for their targeting to mitochondria. In several cases, targeting and sorting information is also contained in non-amino-terminal portions of the precursor protein. Nucleoside triphosphates are required to keep precursors in an import-competent (unfolded) conformation. The precursors bind to specific receptor proteins on the mitochondrial surface and interact with a general insertion protein (GIP) in the outer membrane. The initial interaction of the precursor with the inner membrane requires the mitochondrial membrane potential (delta psi) and occurs at contact sites between outer and inner membranes. Completion of translocation into the inner membrane or matrix is independent of delta psi. The presequences are cleaved off by the processing peptidase in the mitochondrial matrix. In several cases, a second proteolytic processing event is performed in either the matrix or in the intermembrane space. Other modifications can occur such as the addition of prosthetic groups (e.g., heme or Fe/S clusters). Some precursors of proteins of the intermembrane space or the outer surface of the inner membrane are retranslocated from the matrix space across the inner membrane to their functional destination ('conservative sorting'). Finally, many proteins are assembled in multi-subunit complexes. Exceptions to this general import pathway are known. Precursors of outer membrane proteins are transported directly into the outer membrane in a receptor-dependent manner. The precursor of cytochrome c is directly translocated across the outer membrane and thereby reaches the intermembrane space. In addition to the general sequence of events which occurs during mitochondrial protein import, current research focuses on the molecules themselves that are involved in these processes.
Topics: Amino Acid Sequence; Animals; Biological Transport; Carrier Proteins; Cytosol; Energy Metabolism; Intracellular Membranes; Mitochondria; Molecular Sequence Data; Peptide Hydrolases; Protein Precursors; Proteins
PubMed: 2642391
DOI: 10.1016/0304-4157(89)90002-6 -
Foods (Basel, Switzerland) Jun 2021Heterocyclic aromatic amines (HAAs) are potent carcinogenic compounds induced by the Maillard reaction in well-done cooked meats. Free amino acids, protein, creatinine,... (Review)
Review
Heterocyclic aromatic amines (HAAs) are potent carcinogenic compounds induced by the Maillard reaction in well-done cooked meats. Free amino acids, protein, creatinine, reducing sugars and nucleosides are major precursors involved in the production of polar and non-polar HAAs. The variety and yield of HAAs are linked with various factors such as meat type, heating time and temperature, cooking method and equipment, fresh meat storage time, raw material and additives, precursor's presence, water activity, and pH level. For the isolation and identification of HAAs, advanced chromatography and spectroscopy techniques have been employed. These potent mutagens are the etiology of several types of human cancers at the ng/g level and are 100- to 2000-fold stronger than that of aflatoxins and benzopyrene, respectively. This review summarizes previous studies on the formation and types of potent mutagenic and/or carcinogenic HAAs in cooked meats. Furthermore, occurrence, risk assessment, and factors affecting HAA formation are discussed in detail. Additionally, sample extraction procedure and quantification techniques to determine these compounds are analyzed and described. Finally, an overview is presented on the promising strategy to mitigate the risk of HAAs by natural compounds and the effect of plant extracts containing antioxidants to reduce or inhibit the formation of these carcinogenic substances in cooked meats.
PubMed: 34202792
DOI: 10.3390/foods10071466