International Review of Cytology (eBook)

A Survey of Cell Biology

Kwang W. Jeon (Herausgeber)

eBook Download: PDF

1999 | 1. Auflage
326 Seiten
Elsevier Science (Verlag)
978-0-08-085729-9 (ISBN)

Infos

International Review of Cytology presents current advances and comprehensive reviews in cell biology-both plant and animal. Articles address structure and control of gene expression, nucleocytoplasmic interactions, control of cell development and differentiation, and cell transformation and growth. Authored by some of the foremost scientists in the field, each volume provides up-to-date information and directions for future research.

Key Features
* Organellar RNA Polymerases of Higher Plants
* Eukaryotic Transmembrane Solution Transport Systems
* Neural Plasticity in the Adult Insect Brain
* Passive Membrane Permeation
* Plasmodesmata and Cell-to-Cell Communication in Plants

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International Review of Cytology presents current advances and comprehensive reviews in cell biology-both plant and animal. Articles address structure and control of gene expression, nucleocytoplasmic interactions, control of cell development and differentiation, and cell transformation and growth. Authored by some of the foremost scientists in the field, each volume provides up-to-date information and directions for future research. - Organellar RNA Polymerases of Higher Plants- Eukaryotic Transmembrane Solution Transport Systems- Neural Plasticity in the Adult Insect Brain- Passive Membrane Permeation- Plasmodesmata and Cell-to-Cell Communication in Plants

Inhalt

Front Cover 1
International Review of Cytology: A Survey of Cell Biology 4
Copyright Page 5
Contents 6
Contributors 10
Chapter 1. Organellar RNA Polymerases of Higher Plants 12
I. Introduction 12
II. The Mitochondrial RNA Polymerase 13
III. The Chloroplast RNA Polymerases 26
IV. Evolution of Plant Phage-Type RNAPs 46
V. Concluding Remarks 54
References 56
Chapter 2. Eukaryotic Transmembrane Solute Transport Systems 72
I. Introduction 73
II. Transport Nomenclature 76
III. The Transport Commission System of Transporter Classification 78
IV. Eukaryotic-Specific Families of Transporters 105
V. Transporters Encoded within the Yeast Genome 134
VI. Transport Proteins for Which High Resolution Three-Dimensional Structures Are Available 136
VII. Concluding Remarks 137
References 139
Chapter 3. Neural Plasticity in the Adult Insect Brain and Its Hormonal Control 148
I. Introduction 148
II. Adult Insect Endocrinology 150
III. Behavioral Plasticity and Its Hormonal Control 155
IV. Neural Plasticity 160
V. Concluding Remarks 172
References 174
Chapter 4. Mechanism of Action of P-Glycoprotein in Relation to Passive Membrane Permeation 186
I. Introduction 187
II. Mechanism of Transbilayer Movement of Drugs 193
III. Drug Adsorption to the Plasma Membrane 207
IV. Stoichiometry of Pgp-Mediated ATP-Hydrolysis to Drug Transport 209
V. An Integrative Model of Drug Transport in MDR Cells 218
VI. Is the Multidrug Transporter a Flippase? 227
VII. Mechanism of Pgp Modulation 234
VIII. Concluding Remarks 243
Appendix: Mathematica Model of Drug Transport into and out of a Cell 244
References 251
Chapter 5. Plasmodesmata and Cell-to-Cell Communication in Plants 262
I. Introduction 262
II. Plasmodesma, a Supramolecular Complex 263
III. Plasmodesmata in Intercellular Trafficking of Proteins and Nucleic Acids 270
IV. Intercellular Macromolecular Trafficking in Animals: Parallel Mechanisms and Functions with Trafficking in Plants 290
V. Plasmodesmata and Plant Developmental Domains 293
VI. Secondary Plasmodesmata and Modification of Existing Plasmodesmata 301
VII. Some Evolutionary Aspects of Cell-to-Cell Communication 309
VIII. Concluding Remarks 314
References 315
Index 330

Textauszug

Eukaryotic Transmembrane Solute Transport Systems

Milton H. Saier, Jr.1    Department of Biology, University of California at San Diego, La Jolla, California 92093-0116
1 Phone: [phone]; fax: [phone] email address: [e-mail]

Abstract

A comprehensive classification system for transmembrane molecular transporters has been proposed. This system is based on (i) mode of transport and energy-coupling mechanism, (ii) protein phylogenetic family, (iii) phylogenetic cluster, and (iv) substrate specificity. The proposed “Transport Commission” (TC) system is superficially similar to that implemented decades ago by the Enzyme Commission for enzymes, but it differs from the latter system in that it uses phylogenetic and functional data for classification purposes. Very few families of transporters include members that do not function exclusively in transport. Analyses reported reveal that channels, primary carriers, secondary carriers (uni-, sym-, and antiporters), and group translocators comprise distinct categories of transporters, and that transport mode and energy coupling are relatively immutable characteristics. By contrast, substrate specificity and polarity of transport are often readily mutable. Thus, with very few exceptions, a unified family of transporters includes members that function by a single transport mode and energy-coupling mechanism although a variety of substrates may be transported with either inwardly or outwardly directed polarity. The TC system allows cross-referencing according to substrates transported and protein sequence database accession numbers. Thus, familial assignments of newly sequenced transport proteins are facilitated. In this article I examine families of transporters that are eukaryotic specific. These families include (i) channel proteins, mostly from animals; (ii) facilitators and secondary active transport carriers; (iii) a few ATP-dependent primary active transporters; and (iv) transporters of unknown mode of action or energy-coupling mechanism. None of the several ATP-independent primary active transport energy-coupling mechanisms found in prokaryotes is represented within the eukaryotic-specific families. The analyses reported provide insight into transporter families that may have arisen in eukaryotes after the separation of eukaryotes from archaea and bacteria. On the basis of the reported analyses, it is suggested that the horizontal transfer of genes encoding transport proteins between eukaryotes and members of the other two domains of life occurred very infrequently during evolutionary history.

KEY WORDS

Transport systems

Protein families

Eukaryotes

Phylogeny

Energy coupling

Transporters

I Introduction

Transport systems serve the cell in numerous capacities (Paulsen et al., 1998a,b; Saier, 1998, 1999). First, they allow entry of all essential nutrients into the cytoplasmic compartment and subsequently into organelles, allowing metabolism of exogenous sources of carbon, nitrogen, sulfur, and phosphorus. Second, they provide a means for the regulation of metabolite concentrations by catalyzing the excretion of end products of metabolic pathways from organelles and cells. Third, they mediate the active extrusion of drugs and other toxic substances from either the cytoplasm or the plasma membrane. Fourth, they mediate uptake and efflux of ionic species that must be maintained at concentrations that differ drastically from those in the external milieu. The maintenance of conditions conducive to life requires a membrane potential, requisite ion concentration gradients, and appropriate cytoplasmic concentrations of all essential trace minerals that participate as cofactors in metabolic processes. Such conditions are required for the generation of bioelectricity and for enzymatic activity. Fifth, transporters participate in the secretion of proteins, complex carbohydrates, and lipids into and beyond the cytoplasmic membrane, and these macromolecules serve a variety of biologically important roles in protection against environmental insult and predation, in communication with members of the same and different species, and in pathogenesis. Sixth, transport systems allow the transfer of nucleic acids across cell membranes, allowing for genetic exchange between organisms, thereby promoting species diversification. Seventh, transporters facilitate the uptake and release of pheromones, alarmones, hormones, neurotransmitters, and a variety of other signaling molecules that allow a cell to participate in the biological experience of multicellularity. Finally, transport proteins allow living organisms to conduct biological warfare, secreting, for example, antibiotics, antiviral agents, and antifungal agents that may confer upon the organism a selective advantage for survival purposes. Thus, from a functional standpoint, the importance of molecular transport to all facets of life cannot be overestimated.

The importance of transport processes to biological systems was recognized more than half a century ago (Gale and Taylor, 1947; Mitchell, 1949). Thanks largely to concerted efforts on the part of Jacques Monod and coworkers at the Pasteur Institute in Paris, who studied the mechanism of action of the Escherichia coli lactose permease, the involvement of specific carrier proteins in transport became established (Rickenberg et al., 1956; Cohen and Monod, 1957). Since these early studies, tremendous progress has been made in understanding the molecular bases of transport phenomena, and the E. coli lactose permease has frequently been at the forefront. Initially, transport processes were characterized from physiological standpoints using intact cells. Cell “ghosts” in which the cytoplasmic contents had been released by osmotic shock proved useful, particularly as applied to human red blood cells and later to bacteria. Work with such systems provided detailed kinetic descriptions of transport processes, and by analogy with chemical reactions catalyzed by enzymes, the proteinaceous nature of all types of permeases became firmly established. Subsequent biochemical experimentation provided extensive documentation of this suggestion (Kaback, 1974).

With the advent of gene sequencing technologies, the primary structures of permeases first became available. Hydrophobicity analyses of these sequences revealed the strikingly hydrophobic natures of various types of integral membrane transporters (Kyte and Doolittle, 1982; Büchel et al., 1980; Lee and Saier, 1983; Overath and Wright, 1983). Current multidisciplinary approaches are slowly yielding three-dimensional structural information about transport systems. However, since only a few such systems have yielded to X-ray crystallographic analyses (Deisenhofer and Michel, 1991; Unwin, 1995; Tsukihara et al., 1996), we still base our views of solute transport on molecular models that provide reasonable pictures of transport systems and the processes they catalyze without providing absolute assurance of accuracy (Goswitz and Brooker, 1995; Varela and Wilson, 1996; Kaback et al., 1997).

It is well recognized that any two proteins that can be shown to be homologous (i.e., that exhibit sufficient primary and/or secondary structural similarity to establish that they arose from a common evolutionary ancestor) will prove to exhibit strikingly similar three-dimensional structures (Doolittle, 1986). Furthermore, the degree of tertiary structural similarity correlates well with the degree of primary structural similarity. For this reason, phylogenetic analyses allow application of modeling techniques to a large number of related proteins and additionally allow reliable extrapolation from one protein member of a family of known structure to others of unknown structure. Thus, once three-dimensional structural data are available for any one family member, these data can be applied to all other members within limits dictated by their degrees of sequence similarity. The same cannot be assumed for members of two independently evolving families.

Similar arguments apply to mechanistic considerations. Thus, the mechanism of solute transport is likely to be similar for all members of a permease family, and variations upon a specific mechanistic theme will be greatest when the sequence divergence is greatest. By contrast, for members of any two independently evolving permease families, the transport mechanisms may be strikingly different. Knowledge of these considerations allows unified mechanistic deductive approaches to be correctly applied to the largest numbers of transport systems, even when evidence is obtained piecemeal from the study of different systems.

The capacity to deduce and extrapolate structural and mechanistic information illustrates the value of phylogenetic data. However, another benefit that may result from the study of molecular phytogeny is to allow an understanding of the mechanistic restrictions that were imposed on an evolving family due to architectural constraints. Specific architectural features may allow one family to diversify in function with respect to substrate specificity, substrate affinity, velocity of transport, polarity of transport, and even mechanism of energy coupling. By contrast, architectural constraints imposed on a second family may not allow functional diversification. Knowledge of the architectural constraints imposed on a permease...

Produkt-Details

• Erscheint lt. Verlag: 11.5.1999
• Sprache: englisch
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Histologie / Embryologie
• Themenwelt: Studium ► 1. Studienabschnitt (Vorklinik) ► Physiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Zellbiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Zoologie
• Themenwelt: Technik
• ISBN-10: 0-08-085729-9 / 0080857299
• ISBN-13: 978-0-08-085729-9 / 9780080857299