scholarly journals Two Distinct Pathways for Targeting Proteins from the Cytoplasm to the Vacuole/Lysosome

1997 ◽  
Vol 139 (7) ◽  
pp. 1687-1695 ◽  
Author(s):  
Misuzu Baba ◽  
Masako Osumi ◽  
Sidney V. Scott ◽  
Daniel J. Klionsky ◽  
Yoshinori Ohsumi
Keyword(s):  
Biosynthetic Pathway ◽  
Biochemical Analysis ◽  
Protein Transport ◽  
Cellular Level ◽  
Spherical Particles ◽  
Alternate Pathway ◽  
Membrane Bound ◽  
Growing Conditions ◽  
Starvation Conditions ◽  
Intracellular Structure

Stress conditions lead to a variety of physiological responses at the cellular level. Autophagy is an essential process used by animal, plant, and fungal cells that allows for both recycling of macromolecular constituents under conditions of nutrient limitation and remodeling the intracellular structure for cell differentiation. To elucidate the molecular basis of autophagic protein transport to the vacuole/lysosome, we have undertaken a morphological and biochemical analysis of this pathway in yeast. Using the vacuolar hydrolase aminopeptidase I (API) as a marker, we provide evidence that the autophagic pathway overlaps with the biosynthetic pathway, cytoplasm to vacuole targeting (Cvt), used for API import. Before targeting, the precursor form of API is localized mostly in restricted regions of the cytosol as a complex with spherical particles (termed Cvt complex). During vegetative growth, the Cvt complex is selectively wrapped by a membrane sac forming a double membrane-bound structure of ∼150 nm diam, which then fuses with the vacuolar membrane. This process is topologically the same as macroautophagy induced under starvation conditions in yeast (Baba, M., K. Takeshige, N. Baba, and Y. Ohsumi. 1994. J. Cell Biol. 124:903–913). However, in contrast with autophagy, API import proceeds constitutively in growing conditions. This is the first demonstration of the use of an autophagy-like mechanism for biosynthetic delivery of a vacuolar hydrolase. Another important finding is that when cells are subjected to starvation conditions, the Cvt complex is now taken up by an autophagosome that is much larger and contains other cytosolic components; depending on environmental conditions, the cell uses an alternate pathway to sequester the Cvt complex and selectively deliver API to the vacuole. Together these results indicate that two related but distinct autophagy-like processes are involved in both biogenesis of vacuolar resident proteins and sequestration of substrates to be degraded.

Rescue of developmental lens abnormalities in chimaeras of noncataractous and congenital cataractous mice

Development ◽  
1987 ◽  
Vol 99 (4) ◽  
pp. 473-480
Author(s):  
A.L. Muggleton-Harris ◽  
K. Hardy ◽  
N. Higbee
Keyword(s):  
Medical Research ◽  
Congenital Cataract ◽  
Biochemical Analysis ◽  
Growth Regulation ◽  
Cellular Level ◽  
Model System ◽  
Mouse Mutant ◽  
Phenotypic Characteristics ◽  
Cataractous Lens ◽  
Mouse Lens

In the study of the lens of a congenital cataractous mouse mutant (CAT), it has been shown that a loss of growth regulation at the cellular level causes gross lens abnormalities. The phenotypic characteristics of the cataractous mouse lens are similar to those seen in human congenital cataract and thus serves as a model system for medical research. In this present investigation, we have demonstrated that the abnormalities of the congenital cataractous lens can be rescued by forming chimaeras between DBA/2 (a noncataractous strain of mouse) and the CAT mutant. This report describes the histological, cellular and biochemical analysis of the resultant chimaeric eyes, and discusses possible mechanisms by which these results were achieved.

scholarly journals How, with whom and when: an overview of CD147-mediated regulatory networks influencing matrix metalloproteinase activity

2016 ◽  
Vol 36 (1) ◽  
Author(s):  
G. Daniel Grass ◽  
Bryan P. Toole
Keyword(s):  
Matrix Metalloproteinase ◽  
Regulatory Networks ◽  
Protein Transport ◽  
Distant Metastases ◽  
Drug Transporter ◽  
Regulatory Systems ◽  
Membrane Bound ◽  
Membrane Type ◽  
Tumour Initiation ◽  
Metalloproteinase Activity

Matrix metalloproteinases (MMPs) comprise a family of 23 zinc-dependent enzymes involved in various pathologic and physiologic processes. In cancer, MMPs contribute to processes from tumour initiation to establishment of distant metastases. Complex signalling and protein transport networks regulate MMP synthesis, cell surface presentation and release. Earlier attempts to disrupt MMP activity in patients have proven to be intolerable and with underwhelming clinical efficacy; thus targeting ancillary proteins that regulate MMP activity may be a useful therapeutic approach. Extracellular matrix metalloproteinase inducer (EMMPRIN) was originally characterized as a factor present on lung cancer cells, which stimulated collagenase (MMP-1) production in fibroblasts. Subsequent studies demonstrated that EMMPRIN was identical with several other protein factors, including basigin (Bsg), all of which are now commonly termed CD147. CD147 modulates the synthesis and activity of soluble and membrane-bound [membrane-type MMPs (MT-MMPs)] in various contexts via homophilic/heterophilic cell interactions, vesicular shedding or cell-autonomous processes. CD147 also participates in inflammation, nutrient and drug transporter activity, microbial pathology and developmental processes. Despite the hundreds of manuscripts demonstrating CD147-mediated MMP regulation, the molecular underpinnings governing this process have not been fully elucidated. The present review summarizes our present knowledge of the complex regulatory systems influencing CD147 biology and provides a framework to understand how CD147 may influence MMP activity.

scholarly journals Biochemical Analysis of the Biosynthetic Pathway of an Anticancer Tetracycline SF2575

2009 ◽  
Vol 131 (48) ◽  
pp. 17677-17689 ◽  
Author(s):  
Lauren B. Pickens ◽  
Woncheol Kim ◽  
Peng Wang ◽  
Hui Zhou ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Biosynthetic Pathway ◽  
Biochemical Analysis

scholarly journals CtACO1 Overexpression Resulted in the Alteration of the Flavonoids Profile of Safflower

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1128 ◽  
Author(s):  
Yanhua Tu ◽  
Beixuan He ◽  
Songyan Gao ◽  
Dandan Guo ◽  
Xinlei Jia ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Biosynthetic Pathway ◽  
Metabolic Flux ◽  
Cellular Level ◽  
Vital Role ◽  
Acid Oxidase ◽  
Hydroxysafflor Yellow A ◽  
Flavonoid Biosynthetic Pathway ◽  
Varying Environments ◽  
Plant Acclimatization

Background: Flavonoids with various structures play a vital role in plant acclimatization to varying environments as well as in plant growth, development, and reproduction. Exogenous applications of ethylene and 1-aminocyclopropane carboxylic acid (ACC), could affect the accumulation of flavonoids. Very few attempts have been made to investigate the effect of 1-aminocyclopropane carboxylic acid oxidase (ACO), a unique enzyme that catalyzes ACC to ethylene, on genes and metabolites in the flavonoid biosynthetic pathway. In this study, two ACOs in safflower (CtACOs) were cloned, and then transgenic safflower with overexpressed CtACO1 was generated through the Agrobacterium-mediated floral dipping method. Results: CtACO1 and CtACO2 were both characterized by the 2-oxoglutarate binding domain RxS and the ferrous iron binding site HxDxnH as ACOs from other plants. However, the transcript levels of CtACO1 in flowers at stages I, II, III, and IV were all higher than those of CtACO2. At the cellular level, by using electroporation transformation, CtACO1 was found to be localized at the cytomembrane in onion epidermal cells. CtACO1 overexpression had varying effects on genes involved in the ethylene and flavonoid biosynthetic pathways. The metabolites analysis showed that CtACO1 overexpression lines had a higher accumulation of quercetin and its glycosylated derivatives (quercetin 3-β-d-glucoside and rutin). In contrast, the accumulation of quinochalcones (hydroxysafflor yellow A and carthamin), kaempferol glycosylated derivatives (kaempferol-3-O-β-rutinoside and kaempferol-3-O-β-d-glucoside), apigenin, and luteolin in CtACO1 overexpression lines were decreased. Conclusion: This study confirmed the feasibility of applying the floral dipping method to safflower and showed a novel regulatory effect of CtACO1 in the flavonoid biosynthetic pathway. It provides hypothetical and practical groundwork for further research on regulating the overall metabolic flux of flavonoids in safflower, particularly hydroxysafflor yellow A and other quinochalcones, by using appropriate genetic engineering strategies.

scholarly journals THE MEMBRANE ATTACK MECHANISM OF COMPLEMENT

1973 ◽  
Vol 138 (2) ◽  
pp. 438-451 ◽  
Author(s):  
William P. Kolb ◽  
Hans J. Müller-Eberhard
Keyword(s):  
Cell Surface ◽  
Target Cell ◽  
Complement Activation ◽  
Binding Sites ◽  
Sedimentation Coefficient ◽  
Cytolytic Activity ◽  
Stable Complex ◽  
Free Solution ◽  
Alternate Pathway ◽  
Membrane Bound

The membrane attack mechanism of complement, C5 to C9, has previously been postulated to associate on the target cell surface to a stable decamolecular complex with a calculated mol wt of 995,000. A soluble and stable complex consisting of C5, C6, C7, C8, and C9 has now been demonstrated to arise as a consequence of complement activation by the classical or alternate pathway. It has a sedimentation coefficient of 22.5S and a mol wt of 1 million daltons, and it migrates on electrophoresis at pH 8.6 as an α-globulin. The stable and soluble C5b-9 complex cannot bind to erythrocytes and has no demonstrable cytolytic activity. However, due to partially unsaturated binding sites for C9, it can bind additional C9 and thus function as an inhibitor of lysis of EAC1-8 by C9. These results support the concept according to which the membrane-bound attack system of complement represents a stable, decamolecular assembly of C5b-9. Unlike its analogue in free solution, the membrane-bound complex is cytolytically active.

Plastoquinone-9 biosynthesis in cyanobacteria differs from that in plants and involves a novel 4-hydroxybenzoate solanesyltransferase

2012 ◽  
Vol 442 (3) ◽  
pp. 621-629 ◽  
Author(s):  
Radin Sadre ◽  
Christian Pfaff ◽  
Stephan Buchkremer
Keyword(s):  
Biosynthetic Pathway ◽  
In Vitro Assays ◽  
Transport Chain ◽  
In Vivo Labelling ◽  
Membrane Bound ◽  
Transformation Processes ◽  
Synechocystis Sp

PQ-9 (plastoquinone-9) has a central role in energy transformation processes in cyanobacteria by mediating electron transfer in both the photosynthetic as well as the respiratory electron transport chain. The present study provides evidence that the PQ-9 biosynthetic pathway in cyanobacteria differs substantially from that in plants. We identified 4-hydroxybenzoate as being the aromatic precursor for PQ-9 in Synechocystis sp. PCC6803, and in the present paper we report on the role of the membrane-bound 4-hydroxybenzoate solanesyltransferase, Slr0926, in PQ-9 biosynthesis and on the properties of the enzyme. The catalytic activity of Slr0926 was demonstrated by in vivo labelling experiments in Synechocystis sp., complementation studies in an Escherichia coli mutant with a defect in ubiquinone biosynthesis, and in vitro assays using the recombinant as well as the native enzyme. Although Slr0926 was highly specific for the prenyl acceptor substrate 4-hydroxybenzoate, it displayed a broad specificity with regard to the prenyl donor substrate and used not only solanesyl diphosphate, but also a number of shorter-chain prenyl diphosphates. In combination with in silico data, our results indicate that Slr0926 evolved from bacterial 4-hydroxybenzoate prenyltransferases catalysing prenylation in the course of ubiquinone biosynthesis.

scholarly journals Nitrite and Nitrous Oxide Reductase Regulation by Nitrogen Oxides in Rhodobacter sphaeroides f. sp.denitrificans IL106

1999 ◽  
Vol 181 (19) ◽  
pp. 6028-6032 ◽  
Author(s):  
Monique Sabaty ◽  
Carole Schwintner ◽  
Sandrine Cahors ◽  
Pierre Richaud ◽  
Andre Verméglio
Keyword(s):  
Nitrous Oxide ◽  
Nitrate Reductase ◽  
Rhodobacter Sphaeroides ◽  
Type Strain ◽  
Biochemical Analysis ◽  
Wild Type Strain ◽  
Nitrous Oxide Reductase ◽  
Wild Type ◽  
Genes Encoding ◽  
Membrane Bound

ABSTRACT We have cloned the nap locus encoding the periplasmic nitrate reductase in Rhodobacter sphaeroides f. sp.denitrificans IL106. A mutant with this enzyme deleted is unable to grow under denitrifying conditions. Biochemical analysis of this mutant shows that in contrast to the wild-type strain, the level of synthesis of the nitrite and N2O reductases is not increased by the addition of nitrate. Growth under denitrifying conditions and induction of N oxide reductase synthesis are both restored by the presence of a plasmid containing the genes encoding the nitrate reductase. This demonstrates that R. sphaeroides f. sp. denitrificans IL106 does not possess an efficient membrane-bound nitrate reductase and that nitrate is not the direct inducer for the nitrite and N2O reductases in this species. In contrast, we show that nitrite induces the synthesis of the nitrate reductase.

scholarly journals Peptidylglycine α-amidating monooxygenase as a therapeutic target or biomarker

2021 ◽  
Author(s):  
David Merkler ◽  
Aidan Hawley ◽  
Betty Eipper ◽  
Richard Mains
Keyword(s):  
Biosynthetic Pathway ◽  
Homo Sapiens ◽  
Growth Promoters ◽  
Therapeutic Value ◽  
Amidation Reaction ◽  
Peptide Biosynthesis ◽  
Membrane Bound ◽  
Peptide Secretion ◽  
Amidated Peptide ◽  
Rate Limiting

Peptides play a key role in controlling many physiological and neurobiological pathways. Many bioactive peptides require a C-terminal α-amide for full activity. The bifunctional enzyme catalyzing α-amidation, peptidylglycine α-amidating monooxygenase (PAM), is the sole enzyme responsible for amidated peptide biosynthesis, from Chlamydomonas reinhardtii to Homo sapiens. Many neuronal and endocrine functions are dependent upon amidated peptides; additional amidated peptides are growth promoters in tumors. The amidation reaction occurs in two steps, glycine α-hydroxylation followed by dealkylation to generate the α-amide product. Currently, most potentially useful inhibitors target the first reaction, which is rate-limiting. PAM is a membrane-bound enzyme that visits the cell surface during peptide secretion. PAM is then used again in the biosynthetic pathway, meaning that cell-impermeable inhibitors or inactivators could have therapeutic value for the treatment of cancer or psychiatric abnormalities. To date, inhibitor design has not fully exploited the structures and mechanistic details of PAM.

scholarly journals Deletion of the mmpL4b gene in the Mycobacterium abscessus glycopeptidolipid biosynthetic pathway results in loss of surface colonization capability, but enhanced ability to replicate in human macrophages and stimulate their innate immune response

Microbiology ◽  
2011 ◽  
Vol 157 (4) ◽  
pp. 1187-1195 ◽  
Author(s):  
Rachid Nessar ◽  
Jean-Marc Reyrat ◽  
Lisa B. Davidson ◽  
Thomas F. Byrd
Keyword(s):  
Pathogenic Bacteria ◽  
Biosynthetic Pathway ◽  
Gene Knockout ◽  
Cellular Level ◽  
Mycobacterium Abscessus ◽  
Bacterial Gene ◽  
Human Macrophages ◽  
Knockout Mutants ◽  
A Cell ◽  
Toll Like Receptor 2

Mycobacterium abscessus is considered to be the most virulent of the rapidly growing mycobacteria. Generation of bacterial gene knockout mutants has been a useful tool for studying factors that contribute to virulence of pathogenic bacteria. Until recently, the optimal genetic approach to generation of M. abscessus gene knockout mutants was not clear. Based on the recent identification of genetic recombineering as the preferred approach, a M. abscessus mutant was generated in which the gene mmpL4b, critical to glycopeptidolipid synthesis, was deleted. Compared to the previously well-characterized parental strain 390S, the mmpL4B deletion mutant had lost sliding motility and the ability to form biofilm, but acquired the ability to replicate in human macrophages and stimulate macrophage Toll-like receptor 2. This study demonstrates that deletion of a gene associated with expression of a cell-wall lipid can result in acquisition of an immunostimulatory, invasive bacterial phenotype and has important implications for the study of M. abscessus pathogenesis at the cellular level.

Molecular interactions within the plant TOC complex

2009 ◽  
Vol 390 (8) ◽  
Author(s):  
Maik S. Sommer ◽  
Enrico Schleiff
Keyword(s):  
Molecular Interactions ◽  
Protein Transport ◽  
Protein Import ◽  
Current Knowledge ◽  
Transport Processes ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Molecules ◽  
Membrane Bound ◽  
Cellular Compartments

Abstract Protein transport, especially into different cellular compartments, is a highly coordinated and regulated process. The molecular machineries which carry out these transport processes are highly complex in structure, function, and regulation. In the case of chloroplasts, thousands of protein molecules have been estimated to be transported across the double-membrane bound envelope per minute. In this brief review, we summarize current knowledge about the molecular interplay during precursor protein import into chloroplasts, focusing on the initial events at the outer envelope.

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