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Author: Mart Patrick Hensley
Publisher:
ISBN:
Category : Biochemistry
Languages : en
Pages : 80
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Book Description
The homeostasis of transition metal ions is critical to the survival of all organisms. Zinc (Zn(II)) is one of the most important transition metals found in biological systems; however, the homeostasis of this metal is poorly understood. Previous studies have shown that intracellular Zn(II) levels in E. coli are in the low millimolar range, yet there is less than one "free" (unbound) Zn(II) ion per cell. There must exist in the E. coli cell a mechanism for the delivery and insertion of Zn(II) into proteins. The cytoplasmic transport of other transitions metals, such as copper, iron, nickel, manganese, and arsenic, is accomplished by a group of proteins called metallochaperones. No such metallochaperone has been identified for Zn(II). Since none of the available models for intracellular Zn(II) transport are able to explain adequately Zn(II) homeostasis in E. coli, we hypothesized a new model. This model proposes that Zn(II) is delivered to Zn(II) metalloproteins as the proteins are translated and exiting the ribosome. In the co-translational model for Zn(II) homeostasis, the first datum that must be accounted for is the constant presence of 0.2 mM Zn(II) in E. coli. In Chapter 2 it is shown that the ribosome binds significant amounts of Zn(II). This ribosomal storage accounts for millimolar amounts of intracellular Zn(II). In Chapters 3 and 4 studies on several ribosomal proteins (L31, L13, L22, L24, and L29) are presented in an effort to identify Zn(II) binding proteins that could transfer Zn(II) to nascent proteins. Our data show that soluble L31 adopts a unique Zn(II) binding motif containing one cysteine and histidine. This Zn(II) binding site is reminiscent of the Cu(I) binding site of ATX1, a copper metallochaperone. Close examination of the E. coli ribosome crystal structures shows that L31 does not bind Zn(II) with the same binding site as in solution. By accounting for all known data about Zn(II) homeostasis in E. coli, it is hypothesized that ribosomal protein L31, while in solution and not bound to the ribosome, acts as a Zn(II) metallochaperone, delivering Zn(II) to nascent proteins as they exit the ribosome.
Author: Mart Patrick Hensley
Publisher:
ISBN:
Category : Biochemistry
Languages : en
Pages : 80
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Book Description
The homeostasis of transition metal ions is critical to the survival of all organisms. Zinc (Zn(II)) is one of the most important transition metals found in biological systems; however, the homeostasis of this metal is poorly understood. Previous studies have shown that intracellular Zn(II) levels in E. coli are in the low millimolar range, yet there is less than one "free" (unbound) Zn(II) ion per cell. There must exist in the E. coli cell a mechanism for the delivery and insertion of Zn(II) into proteins. The cytoplasmic transport of other transitions metals, such as copper, iron, nickel, manganese, and arsenic, is accomplished by a group of proteins called metallochaperones. No such metallochaperone has been identified for Zn(II). Since none of the available models for intracellular Zn(II) transport are able to explain adequately Zn(II) homeostasis in E. coli, we hypothesized a new model. This model proposes that Zn(II) is delivered to Zn(II) metalloproteins as the proteins are translated and exiting the ribosome. In the co-translational model for Zn(II) homeostasis, the first datum that must be accounted for is the constant presence of 0.2 mM Zn(II) in E. coli. In Chapter 2 it is shown that the ribosome binds significant amounts of Zn(II). This ribosomal storage accounts for millimolar amounts of intracellular Zn(II). In Chapters 3 and 4 studies on several ribosomal proteins (L31, L13, L22, L24, and L29) are presented in an effort to identify Zn(II) binding proteins that could transfer Zn(II) to nascent proteins. Our data show that soluble L31 adopts a unique Zn(II) binding motif containing one cysteine and histidine. This Zn(II) binding site is reminiscent of the Cu(I) binding site of ATX1, a copper metallochaperone. Close examination of the E. coli ribosome crystal structures shows that L31 does not bind Zn(II) with the same binding site as in solution. By accounting for all known data about Zn(II) homeostasis in E. coli, it is hypothesized that ribosomal protein L31, while in solution and not bound to the ribosome, acts as a Zn(II) metallochaperone, delivering Zn(II) to nascent proteins as they exit the ribosome.
Author: Joseph Ingram
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: W. Maret
Publisher: Springer Science & Business Media
ISBN: 9401737282
Category : Science
Languages : en
Pages : 232
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Book Description
Chapters in this book review the remarkable advances in the field of zinc biology over the last decade. Zinc is essential for life, in particular for growth and development, through its role in hundreds of zinc enzymes and thousands of zinc proteins. Its catalytic, structural, and regulatory functions in these proteins impact metabolism, gene expression, and signal transduction, including neurotransmission. Among the micronutrients, zinc may rank with iron as to its importance for public health. The topics covered range from single molecules to cells and to whole organisms: the chemistry, design, and application of fluorophores for the determination of cellular zinc; the role of zinc in proliferation, differentiation, and apoptosis of cells; proteins that transport, sense, and distribute zinc and together form a cellular homeostatic system; the coordination chemistry of zinc in metalloproteins; the role of zinc in the brain as a neuromodulator/transmitter; the dependence of the immune system on zinc; zinc homeostasis in the whole human body.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Cellular zinc homeostasis is essential to human health. Zinc transporters transport zinc ions into and out of cells to maintain cellular zinc concentrations in a narrow range. Several membrane proteins have been shown to facilitate transmembrane fluxes of zinc ions, however, structures of these zinc transporters are unknown. The purpose of this work is to express, purify and crystallize a Zinc transporter, ZitB for crystallographic studies. ZitB was over-expressed as a His-tagged membrane protein using a pET15b expression vector hosted in E. coli BL21 cells. Purification of ZitB was achieved by preparation of ZitB-containing membrane vesicles, followed by detergent extraction, and completed with Ni-NTA metal affinity and size exclusion chromatography. The molecular identity of the purified ZitB was confirmed by mass spectrometry, which showed the expected molecular weight of 35.2kDa. Crystallization trials of ZitB were conducted at 20 oC, using a series of low molecular weight PEGs as precipitants. Micro-crystals were grown in 25% PEG 1K, whereas only amorphous precipitations were observed in PEG 400 and 600. In conclusion, this work yielded highly purified ZitB protein and defined an initial crystallization condition for ZitB.
Author: Jose M. Arguello
Publisher: Academic Press
ISBN: 0123943906
Category : Science
Languages : en
Pages : 478
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Book Description
This volume of Current Topics in Membranes focuses on metal transmembrane transporters and pumps, a recently discovered family of membrane proteins with many important roles in the physiology of living organisms. The book summarizes the most recent advances in the field of metal ion transport and provides a broad overview of the major classes of transporters involved in homeostasis of heavy metals. Various families of the transporters and metal specificities are discussed with the focus on the structural and mechanistic aspects of their function and regulation. The reader will access information obtained through a variety of approaches ranging from X-ray crystallography to cell biology and bioinformatics, which have been applied to transporters identified in diverse biological systems, such as pathogenic bacteria, plants, humans and others. Field is cutting-edge and a lot of the information is new to research community Wide breadth of topic coverage Contributors of high renown and expertise
Author: James Allen Easton
Publisher:
ISBN:
Category : Escherichia coli
Languages : en
Pages : 168
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Book Description
Transition metal ion homeostasis is absolutely crucial for the survival of all organisms. Zinc (Zn(II)) is perhaps one of the most important, yet least studied transition metals. Previous studies indicate that intracellular Zn(II) levels in E. coli are in the low millimolar range, yet there is less than one "free" Zn(II) ion per cell. All of the intracellular Zn(II) must then be bound and Zn(II) must be delivered from transporters and inserted into Zn(II)-metalloproteins. The cytoplasmic transport of transition metals, such as copper, iron, nickel, manganese, and arsenic, is accomplished by a group of proteins called metallochaperones. No such metallochaperone has been identified for Zn(II). In an effort to identify the Zn(II) metallochaperones in E. coli, proteomic and genomic studies were conducted. Proteomic studies were used to probe for the time-dependent response of E. coli to stress by Zn(II) excess. Genomic studies were used to probe for the transcriptional response of E. coli to stress by Zn(II) excess and deficiency. Several Zn(II)-metallochaperone candidates were identified, and these proteins were cloned, over-expressed, purified, and characterized. Trigger factor was found to be down-regulated at the proteomic level in response to excess Zn(II). Over-expression and characterization of trigger factor show that it tightly binds 0.5 Zn(II)/monomer; however, spectroscopic studies showed that Zn(II) binding is most likely adventitious. GatY/GatZ Zn(II)-responsive proteins that are part of the galactitol catabolic pathway. GatY was over-expressed and shown to bind 2 Zn(II) equivalents per enzyme. GatZ, reported to be necessary for GatY function, was tested for Zn(II)-binding and shown to not bind Zn(II). A transcript found to be highly up-regulated was ykgM. We cloned and over-expressed YkgM to elucidate why it is highly responsive to Zn(II). We determined that YkgM does not bind Zn(II), and may substitute for Zn(II)-containing ribosomal protein L31 in Zn(II)-limiting conditions. ZnuA was cloned, over-expressed, purified, and characterized. We found that ZnuA tightly binds 2 equivalents of Zn(II) per monomer. Our proteomic and genomic data suggest that there are no soluble, cytoplasmic Zn(II) metallochaperones in E. coli. Based on this conclusion, a novel model is hypothesized that explains Zn(II) transport in E. coli cytoplasm.
Author: Marcelo E. Tolmasky
Publisher: John Wiley & Sons
ISBN: 1555818986
Category : Science
Languages : en
Pages : 512
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Book Description
Explore the remarkable discoveries in the rapidly expanding field of plasmid biology Plasmids are integral to biological research as models for innumerable mechanisms of living cells, as tools for creating the most diverse therapies, and as crucial helpers for understanding the dissemination of microbial populations. Their role in virulence and antibiotic resistance, together with the generalization of "omics" disciplines, has recently ignited a new wave of interest in plasmids. This comprehensive book contains a series of expertly written chapters focused on plasmid biology, mechanistic details of plasmid function, and the increased utilization of plasmids in biotechnology and pharmacology that has occurred in the past decade. Plasmids: Biology and Impact in Biotechnology and Discovery serves as an invaluable reference for researchers in the wide range of fields and disciplines that utilize plasmids and can also be used as a textbook for upper-level undergraduate and graduate courses in biotechnology and molecular biology.
Author: Scott Edward Gabriel
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Zinc is an essential nutrient due to its role as a structural co-factor for protein folding and as a catalytic co-factor for many enzymes. However, if this nutrient accumulates over a given threshold, it can become toxic to the cell. For these reasons, it is absolutely critical for cell survival that zinc homeostasis be tightly controlled. In Bacillus subtilis, a model Gram positive organism, the response to zinc limitation is mediated by Zur which acts as a classical repressor when Zinc is present. The Zur regulon has been characterized and currently contains ten genes all suspected or known to contribute to the zinc starvation response. Classically this response was thought of in terms of obtaining external zinc by high affinity pumps. In part, the work presented within will show that our understanding bacterial metal ion homeostasis is expanding. We now understand that in addition to uptake as a metal limitation response, cells also create duplicates of zinc requiring proteins which have altered metal co-factor specificity, a mechanism we classify as substitution. Finally, bacteria use mobilization as a response mechanism by creating conditions in which zinc containing proteins are replaced and the zinc which they contained is used for continued growth in zinc limiting conditions. The work presented here shows a cross-section of the molecular mechanisms Zur employs to achieve zinc homeostasis in Bacillus subtilis. Starting at the protein biochemistry level, I will present studies aimed at addressing how Zur senses zinc. This work uses a site directed mutagenesis approach to identify amino acid residues which make up the three conserved zinc binding pockets within the Zur protein and how each contributes to Zur's function. Second, after understanding how the protein senses zinc, I sought to understand how Zur regulated one of the uncharacterized members of its regulon, the yciC gene. In addition to elucidating the regulation of the unique promoter structure of yciC, I also show that Zur binds a consensus 9-1-9 inverted repeat. Finally at a physiological level, I studied the three ribosomal genes under the control of Zur to understand their contribution towards the zinc starvation response.
Author: Toshiyuki Fukada
Publisher: Springer Nature
ISBN: 9811505578
Category : Medical
Languages : en
Pages : 412
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Book Description
This book, now in an extensively revised second edition, describes the crucial role of zinc signaling in biological processes on a molecular and physiological basis. Global leaders in the field review the latest knowledge, including the very significant advances in understanding that have been achieved since publication of the first edition. Detailed information is provided on all the essentials of zinc signaling, covering molecular aspects and the roles of zinc transporters, the zinc sensing receptor, and metallothioneins. Detection techniques for zinc signals, involving genetically encoded and chemical probes, are also described. The critical contributions of the zinc signal in maintaining health and the adverse consequences of any imbalance in the signal are then thoroughly addressed. Here, readers will find up-to-date information on the significance of the zinc signal in a wide range of conditions, including cardiovascular disorders, neurodegenerative diseases, diabetes, autoimmune diseases, inflammatory conditions, skin disease, osteoarthritis, and cancer. The book will be of value for researchers, clinicians, and advanced students.
Author: Dietrich H. Nies
Publisher: Springer Science & Business Media
ISBN: 3540697713
Category : Science
Languages : en
Pages : 455
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Book Description
This book covers allocation of metals in cells, metal transporter, storage and metalloregulatory proteins, cellular responses to metal ion stress, transcription of genes involved in metal ion homeostasis, uptake of essential metals, metal efflux and other detoxification mechanisms. The book also discusses metal bioreporters for the nanomolar range of concentration and tools to address the metallome. In addition, coverage details specific metals.
