scholarly journals The Vibrio cholerae SpeG Spermidine/Spermine N-Acetyltransferase Allosteric Loop and β6-β7 Structural Elements Are Critical for Kinetic Activity

2021 ◽  
Vol 8 ◽  
Author(s):  
Van Thi Bich Le ◽  
Sofiya Tsimbalyuk ◽  
Ee Qi Lim ◽  
Allan Solis ◽  
Darwin Gawat ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Intracellular Signaling ◽  
Point Mutations ◽  
Structural Evolution ◽  
Transport Systems ◽  
Enzyme Kinetic ◽  
Structural Elements ◽  
Allosteric Site ◽  
Kinetic Activity ◽  
Domains Of Life

Polyamines regulate many important biological processes including gene expression, intracellular signaling, and biofilm formation. Their intracellular concentrations are tightly regulated by polyamine transport systems and biosynthetic and catabolic pathways. Spermidine/spermine N-acetyltransferases (SSATs) are catabolic enzymes that acetylate polyamines and are critical for maintaining intracellular polyamine homeostasis. These enzymes belong to the Gcn5-related N-acetyltransferase (GNAT) superfamily and adopt a highly conserved fold found across all kingdoms of life. SpeG is an SSAT protein found in a variety of bacteria, including the human pathogen Vibrio cholerae. This protein adopts a dodecameric structure and contains an allosteric site, making it unique compared to other SSATs. Currently, we have a limited understanding of the critical structural components of this protein that are required for its allosteric behavior. Therefore, we explored the importance of two key regions of the SpeG protein on its kinetic activity. To achieve this, we created various constructs of the V. cholerae SpeG protein, including point mutations, a deletion, and chimeras with residues from the structurally distinct and non-allosteric human SSAT protein. We measured enzyme kinetic activity toward spermine for ten constructs and crystallized six of them. Ultimately, we identified specific portions of the allosteric loop and the β6-β7 structural elements that were critical for enzyme kinetic activity. These results provide a framework for further study of the structure/function relationship of SpeG enzymes from other organisms and clues toward the structural evolution of members of the GNAT family across domains of life.

scholarly journals Globalization of the transport system of the agro-industrial complex in the conditions of modern society

2020 ◽  
Vol 176 ◽  
pp. 05020
Author(s):  
M.A. Ananyev ◽  
Zh.Yu Bakaeva ◽  
O.L. Matveeva ◽  
I.V. Steklova ◽  
E.N. Shchegoleva
Keyword(s):  
Transport System ◽  
Modern Society ◽  
Transport Systems ◽  
Industrial Complex ◽  
Structural Elements ◽  
Economic Space ◽  
Different Types ◽  
Food Market ◽  
Temporal And Spatial ◽  
Favorable Conditions

The article deals with the problem of transportation of agricultural products. The main causes of problems in this area are identified. The mechanism of creating favorable conditions in the system of globalization relations of the modern economy is analyzed. The fundamental elements in the transport system are competition orientation and information ownership over a certain period of time. Globalization involves the integration of different types of transport systems at the sectoral characteristics. The purpose of the research is to study the essence, meaning and prospects of the concept of “economic transport space in the national food supply system" in the processes of food market globalization. The main indicators of the “economic space" are: first, to determine the parameters that characterize the economic transport space, and secondly, to determine the prospects for using its structural elements in the system of transport supply relations, depending on the temporal and spatial components in the modern sector of the economy to provide food for the needs of society.

scholarly journals Vibrio cholerae VciB Mediates Iron Reduction

2017 ◽  
Vol 199 (12) ◽  
Author(s):  
Eric D. Peng ◽  
Shelley M. Payne
Keyword(s):  
Electron Transport ◽  
Vibrio Cholerae ◽  
Ferrous Iron ◽  
Electron Transport Chain ◽  
Iron Reduction ◽  
Iron Transport ◽  
Ferric Iron ◽  
Transport Systems ◽  
Content Type ◽  
Transport Chain

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. V. cholerae thrives within the human host, where it replicates to high numbers, but it also persists within the aquatic environments of ocean and brackish water. To survive within these nutritionally diverse environments, V. cholerae must encode the necessary tools to acquire the essential nutrient iron in all forms it may encounter. A prior study of systems involved in iron transport in V. cholerae revealed the existence of vciB, which, while unable to directly transport iron, stimulates the transport of iron through ferrous (Fe2+) iron transport systems. We demonstrate here a role for VciB in V. cholerae in which VciB stimulates the reduction of Fe3+ to Fe2+, which can be subsequently transported into the cell with the ferrous iron transporter Feo. Iron reduction is independent of functional iron transport but is associated with the electron transport chain. Comparative analysis of VciB orthologs suggests a similar role for other proteins in the VciB family. Our data indicate that VciB is a dimer located in the inner membrane with three transmembrane segments and a large periplasmic loop. Directed mutagenesis of the protein reveals two highly conserved histidine residues required for function. Taken together, our results support a model whereby VciB reduces ferric iron using energy from the electron transport chain. IMPORTANCE Vibrio cholerae is a prolific human pathogen and environmental organism. The acquisition of essential nutrients such as iron is critical for replication, and V. cholerae encodes a number of mechanisms to use iron from diverse environments. Here, we describe the V. cholerae protein VciB that increases the reduction of oxidized ferric iron (Fe3+) to the ferrous form (Fe2+), thus promoting iron acquisition through ferrous iron transporters. Analysis of VciB orthologs in Burkholderia and Aeromonas spp. suggest that they have a similar activity, allowing a functional assignment for this previously uncharacterized protein family. This study builds upon our understanding of proteins known to mediate iron reduction in bacteria.

Theoretical aspects of interaction of flow and structural elements in transport systems

2019 ◽  
pp. 3-7
Author(s):  
Petr Alexeyevich Kozlov ◽  
◽  
Vitaliy Sergeevich Kolokolnikov ◽  
Keyword(s):  
Transport Systems ◽  
Structural Elements

scholarly journals Mechanism of ToxT-Dependent Transcriptional Activation at the Vibrio cholerae tcpA Promoter

2002 ◽  
Vol 184 (20) ◽  
pp. 5533-5544 ◽  
Author(s):  
Robin R. Hulbert ◽  
Ronald K. Taylor
Keyword(s):  
Rna Polymerase ◽  
Vibrio Cholerae ◽  
Transcriptional Activation ◽  
Point Mutations ◽  
Virulence Gene ◽  
Binding Studies ◽  
Virulence Gene Expression ◽  
Terminal Domain ◽  
Truncation Mutation ◽  
Genes Encoding

ABSTRACT The AraC homolog ToxT coordinately regulates virulence gene expression in Vibrio cholerae. ToxT is required for transcriptional activation of the genes encoding cholera toxin and the toxin coregulated pilus, among others. In this work we focused on the interaction of ToxT with the tcpA promoter and investigated the mechanism of ToxT-dependent transcriptional activation at tcpA. Deletion analysis showed that a region from −95 to +2 was sufficient for ToxT binding and activation, both of which were simultaneously lost when the deletion was extended to −63. A collection of point mutations generated by error-prone PCR revealed two small regions required for ToxT-dependent transactivation. Binding studies performed with representative mutations showed that the two regions define sites at which ToxT binds to the tcpA promoter region, most likely as a dimer. Results obtained by using a rpoA truncation mutation showed that ToxT-dependent activation at tcpA involves the C-terminal domain of the RNA polymerase alpha subunit. A model of ToxT-dependent transcriptional activation at tcpA is proposed, in which ToxT interacts with two A-rich regions of tcpA centered at −72 and −51 and requires the alpha C-terminal domain of RNA polymerase.

Structural evolution of the Hemlo greenstone belt in the vicinity of the world-class Hemlo gold deposit

2003 ◽  
Vol 40 (3) ◽  
pp. 395-430 ◽  
Author(s):  
T L Muir
Keyword(s):  
Gold Deposit ◽  
Greenstone Belt ◽  
Structural Evolution ◽  
Small Scale ◽  
Structural Elements ◽  
Shear Sense ◽  
History Of ◽  
Brittle Fractures ◽  
World Class ◽  
Dextral Shear

A complex history of volcano-sedimentary deposition, polyphase strain, multiple intrusive events, and various stages of porphyroblastesis is indicated for the Hemlo gold deposit area within the Hemlo greenstone belt. Structural elements can be assigned to at least six stages of development (D1–D6). D1 generated small-scale folds and low-angle faults (thrusts?) with no planar fabric, except within strain aureoles around the earliest intrusions. D2 was a progressive event resulting from northeast-directed compression, which generated regional, predominantly S-shaped folds (early D2); penetrative planar and linear fabrics, overturned stratigraphy, and formation of an inflection in the strike of the greenstone belt (mid-D2); and development of high-strain zones with dominant sinistral and local dextral shear sense (late D2). D3 was a distinctly separate progressive event resulting from northwest-directed transpression, which generated variably penetrative east- to northeast-striking foliation (S3), ductile dextral shear fabrics, and small-scale Z-shaped folds (early D3), followed by brittle–ductile to brittle development of cataclasite and pseudotachylite in layer-parallel zones (late D3). D4 resulted in contractional kinks and brittle fractures, locally in conjugate sets. D5 and D6 are represented by brittle to brittle–ductile faults, which overprint Paleoproterozoic and Mesoproterozoic dikes, respectively. Four granitoid magmatic events span the interval 2720–2677 Ma, with emplacement mainly during D2, between ca. 2690 and ca. 2684 Ma. A protracted period of regional medium-grade metamorphism likely spanned the D2–D3 stages. The Hemlo gold deposit was emplaced during mid-D2 and was largely controlled by D2 structural elements and competency contrast between rock units.

scholarly journals Towards Understanding of Polymorphism of the G-rich Region of Human Papillomavirus Type 52

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1294 ◽  
Author(s):  
Maja Marušič ◽  
Janez Plavec
Keyword(s):  
Human Papillomavirus ◽  
Snp Analysis ◽  
Nucleotide Polymorphisms ◽  
Structural Elements ◽  
Structural Polymorphism ◽  
Single Nucleotide ◽  
Viral Genomes ◽  
Guanine Residue ◽  
G Quadruplex ◽  
Domains Of Life

The potential to affect gene expression via G-quadruplex stabilization has been extended to all domains of life, including viruses. Here, we investigate the polymorphism and structures of G-quadruplexes of the human papillomavirus type 52 with UV, CD and NMR spectroscopy and gel electrophoresis. We show that oligonucleotide with five G-tracts folds into several structures and that naturally occurring single nucleotide polymorphisms (SNPs) have profound effects on the structural polymorphism in the context of G-quadruplex forming propensity, conformational heterogeneity and folding stability. With help of SNP analysis, we were able to select one of the predominant forms, formed by G-rich sequence d(G3TAG3CAG4ACACAG3T). This oligonucleotide termed HPV52(1–4) adopts a three G-quartet snap back (3 + 1) type scaffold with four syn guanine residues, two edgewise loops spanning the same groove, a no-residue V loop and a propeller type loop. The first guanine residue is incorporated in the central G-quartet and all four-guanine residues from G4 stretch are included in the three quartet G-quadruplex core. Modification studies identified several structural elements that are important for stabilization of the described G-quadruplex fold. Our results expand set of G-rich targets in viral genomes and address the fundamental questions regarding folding of G-rich sequences.

Comparative Study of Two Transport Systems for Vibrio Cholerae

1994 ◽  
Vol 24 (1) ◽  
pp. 35-36 ◽  
Author(s):  
S Estrada ◽  
E Jaramillo ◽  
M Gaviria ◽  
S Ospina
Keyword(s):  
Comparative Study ◽  
Vibrio Cholerae ◽  
Transport Systems

scholarly journals Characterization of Ferric and Ferrous Iron Transport Systems in Vibrio cholerae

2006 ◽  
Vol 188 (18) ◽  
pp. 6515-6523 ◽  
Author(s):  
Elizabeth E. Wyckoff ◽  
Alexandra R. Mey ◽  
Andreas Leimbach ◽  
Carolyn F. Fisher ◽  
Shelley M. Payne
Keyword(s):  
Vibrio Cholerae ◽  
Transport System ◽  
Iron Transport ◽  
Iron Acquisition ◽  
Shigella Flexneri ◽  
Transport Systems ◽  
Infant Mouse ◽  
Mouse Intestine ◽  
Dependent Transport

ABSTRACT Vibrio cholerae has multiple iron acquisition systems, including TonB-dependent transport of heme and of the catechol siderophore vibriobactin. Strains defective in both of these systems grow well in laboratory media and in the infant mouse intestine, indicating the presence of additional iron acquisition systems. Previously uncharacterized potential iron transport systems, including a homologue of the ferrous transporter Feo and a periplasmic binding protein-dependent ATP binding cassette (ABC) transport system, termed Fbp, were identified in the V. cholerae genome sequence. Clones encoding either the Feo or the Fbp system exhibited characteristics of iron transporters: both repressed the expression of lacZ cloned under the control of a Fur-regulated promoter in Escherichia coli and also conferred growth on a Shigella flexneri mutant that has a severe defect in iron transport. Two other ABC transporters were also evaluated but were negative by these assays. Transport of radioactive iron by the Feo system into the S. flexneri iron transport mutant was stimulated by the reducing agent ascorbate, consistent with Feo functioning as a ferrous transporter. Conversely, ascorbate inhibited transport by the Fbp system, suggesting that it transports ferric iron. The growth of V. cholerae strains carrying mutations in one or more of the potential iron transport genes indicated that both Feo and Fbp contribute to iron acquisition. However, a mutant defective in the vibriobactin, Fbp, and Feo systems was not attenuated in a suckling mouse model, suggesting that at least one other iron transport system can be used in vivo.

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