Formation of transmembrane pores is a very effective way of killing cells. It is thus not surprising that many bacterial and eukaryotic toxic agents are pore-forming proteins. Pore formation in a target membrane is a complex process composed of several steps; proteins need to attach to the lipid membrane, possibly aggregate in the plane of the membrane and finally form a pore by inserting part of the polypeptide chain across the lipid bilayer. Structural information about toxins at each stage is indispensible for the biochemical and molecular biological studies that aim to - derstand how pores are formed at the molecular level. There are currently only two Staphylococcus aureus and hemolysin E from Escherichia coli. Therefore, what we know about these proteins was obtained over many years of intense experimentation. We have nevertheless, in the last couple of years, witnessed a significant rise in structural information on the soluble forms of pore-forming proteins. Surprisingly, many unexpected similarities with other proteins were noted, despite extremely low or insignificant sequence similarity. It appears that lipid membrane binding and formation of transmembrane channels is achieved in many cases by a limited repertoire of structures. This book describes how several of the important pore forming toxin families achieve membrane bi- ing and which structural elements are used for formation of transmembrane pores. Our contributors have thus provided the means for a comparative analysis of several unrelated families.

Gregor Anderluh is Associate Professor of Biochemistry at the Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana,
Slovenia. He and his coworkers are studying protein-membrane interactions and how cellular membranes are damaged by proteins. He is a director of the Infrastuctural
Centre for Surface Plasmon Resonance at the University of Ljubljana, where they study molecular interactions and are developing novel approaches on how to study protein binding to membranes. He received his PhD in Biology from University of Ljubljana and did his Postdoctoral at University of Newcastle, United Kingdom.
Jeremy Lakey is Professor of Structural Biochemistry at the Institute for Cell and Molecular Biosciences, University of Newcastle, UK and runs an academic research group based loosely on the theme of protein biophysical chemistry with interests in protein toxins, membranes and bionanotechnology. Following a first degree in Zoology, Jeremy completed a PhD in Membrane Biophysics at the University of East Anglia UK, followed by periods at the Centre de Biophysique Moléculaire, Orléans, France; EMBL, Heidelberg, Germany and the EPFL , Lausanne Switzerland. He is currently an editor of the Biochemical Journal and member of the facility access panel for the ISIS pulsed neutron source, UK.

1. Introduction
Susanne C. Feil, Galina Polekhina, Michael A. Gorman and Michael W. Parker
Abstract
Introduction
Nomenclature
Three?Dimensional Structures of Pore?Forming Proteins
Membrane Binding
Oligomerization
Common Features of Membrane Insertion
Conclusion
2. Energetics of Peptide and Protein Binding to Lipid Membranes
William C. Wimley
Abstract
The Lipid Bilayer Phase
Hydrophobic Interactions
Electrostatic Interactions
Additivity between Electrostatic and Hydrophobic Interactions
The Influence of Peptide and Protein Structure
Specific Interactions
Specificity: The Formation of Ordered Pores
Promiscuity: Membrane?Permeabilization by Interfacial Activity
Conclusion
3. Membrane Association and Pore Formation by Alpha?Helical Peptides
Burkhard Bechinger
Abstract
Introduction
Alamethicin and Other Peptaibols
Cationic Amphipathic Antimicrobial Peptides
Membrane Proteins
Conclusion
4. Role of Membrane Lipids for the Activity of Pore Forming Peptides and Proteins
Gustavo Fuertes, Diana Giménez, Santi Esteban?Martín, Ana J. García?Sáez, Orlando Sánchez and Jesús Salgado
Abstract
Introduction
Membrane Interfaces Are Ideal Binding Sites for Pore?Forming Peptides
and Proteins
A Membrane Foldase Activity Configures Peptide and Protein Active Structures
Role of Lipids in the Formation and Stabilization of Pores
Physical Properties of Polypeptide?Induced Pores Related to the Role of Lipids
Conclusion
5. Cholesterol?Dependent Cytolysins
Robert J.C. Gilbert
Abstract
Functional Studies on CDCs
Membrane binding by CDCs
Pore Formation by CDCs
Proteolipid Pores
Oligomerisation- A Mechanism for Membrane Insertion
Complex Effects of CDCs and Related Protiens
Conclusion
6. Laetiporus sulphureus Lectin and Aerolysin Protein Family
José Miguel Mancheño, Hiroaki Tateno, Daniel Sher and Irwin J. Goldstein
Abstract
Introduction
Pore?Forming Hemolytic Lectins
A New Member within the Aerolysin Family: The Crystal Structure of LSLa
Oligomeric State ofWater?Soluble LSLa
A Common Aerolysin?Like Pore?Forming Module Structure?
Other New Members in the Aerolysin Family: Basic Aerolysin Pore?Forming
Motifs?
Conclusion
7. Interfa cial Interactions of Pore-Forming Colicins
Helen Ridley, Christopher L. Johnson and Jeremy H. Lakey
Abstract
Introduction
Structures
Receptor Binding
Translocation
Crossing the Periplasm
Inner Membrane Inserted Forms
Conclusion
8. Permeabilization of the Outer Mitochondrial Membrane by Bcl?2 Proteins
Ana J. García?Sáez, Gustavo Fuertes, Jacob Suckale and Jesús Salgado
Abstract
Introduction
The Structure of the Bcl?2 Proteins
Pore?Forming Properties of Bcl?2 Proteins
Regulation of MOM Permeabilization by Bcl?2 Proteins
Conclusion
9. Molecular Mechanism of Sphingomyelin?Specific Membrane Binding and Pore Formation by Actinoporins
Biserka Bakra? and Gregor Anderluh
Abstract
Introduction
Structural Properties of Actinoporins
Actinoporins Specifically Bind Sphingomyelin as the First Step in Pore
Formation
Flexibility of the N?Terminal Region is Required for Pore Formation
Pore Formation Involves Nonlamellar Lipid Structures
Similarity to Other Proteins
Conclusion
10. Hemolysin E (HlyE, ClyA, SheA) and Related Toxins
Stuart Hunt, Jeffrey Green and Peter J. Artymiuk
Abstract
Introduction
Regulation of hlyE Expression
Structural Studies on HlyE
Process of Membrane Insertion
HlyE Secretion and Exploitation in Vaccine Development and Tumour
Targeting
HlyE?Like Toxins from Bacillus cereus
Conclusion
11. Pore formation by Cry toxins
Mario Soberón, Liliana Pardo, Carlos Muñóz?Garay, Jorge Sánchez, Isabel Gómez, Helena Porta and Alejandra Bravo
Abstract
Introduction
Mechanism of Action of Cry Toxins
Solubilization and Proteolytic Activation of Cry toxins
Binding Interaction with Receptors
Role of Cry toxin?Receptor Interaction in Toxicity
Oligomerization of Cry toxins
Pore formation
Synergism between Cry and Cyt toxins
Conclusion
12. Role of Hepa ran Sulfa tes and