The Protein Folding Problem And Its Solutions

This book presents a new approach to the Protein Folding Problem. It starts with a clear description of what the protein folding problem involves. Then, it suggests non-conventional answers to some of the questions posed. In particular, it emphasizes the importance of hydrophilic interactions and hydrophilic forces, rather than the hydrophobic effects, for the stability of the native structure of proteins, as well for the speed of the folding process.

A solution to the protein folding problem has eluded researchers for more than 30 years. The stakes are high. Such a solution will make 40,000 more tertiary structures available for immediate study by translating the DNA sequence information in the sequence databases into three-dimensional protein structures. This translation will be indispensable for the analy sis of results from the Human Genome Project, de novo protein design, and many other areas of biotechnological research. Finally, an in-depth study of the rules of protein folding should provide vital clues to the protein fold ing process. The search for these rules is therefore an important objective for theoretical molecular biology. Both experimental and theoretical ap proaches have been used in the search for a solution, with many promising results but no general solution. In recent years, there has been an exponen tial increase in the power of computers. This has triggered an incredible outburst of theoretical approaches to solving the protein folding problem ranging from molecular dynamics-based studies of proteins in solution to the actual prediction of protein structures from first principles. This volume attempts to present a concise overview of these advances. Adrian Roitberg and Ron Elber describe the locally enhanced sam pling/simulated annealing conformational search algorithm (Chapter 1), which is potentially useful for the rapid conformational search of larger molecular systems.

The protein folding problem refers to the correlation of a protein's amino acid sequence and its native three-dimensional structure which is essential for functionality. It still constitutes one of the major challenges in computational biology. One commonly studied model for the protein folding problem is the HP lattice model in which proteins are considered in a fairly abstract representation. However, the HP model proteins exhibit significant parallels to proteins occurring in nature. The solution of the HP lattice mode as a combinatorial optimization problem has been proven to be NP-complete, and there have already been developed various different approaches for efficient algorithms. We study an integer programming formulation of the problem. Starting with an analysis of this model, where we concentrate on symmetry issues, we show how the model can be consolidated by exploiting symmetry properties of the underlying lattice. The main focus lies in the development of specific components of a branch-and-cut framework for the computation of solutions for the HP model by means of integer programming methods. In order to understand the structure of the model, we perform a series of polyhedral studies from which we derive two main classes of cutting planes. Furthermore, we exploit the knowledge of folding principles which are also valid for HP model proteins for the development of related branching strategies. For the solution of a special class of instances, we present an implementation of a genetic algorithm for the generation of primal feasible start solutions. Finally, we document the performance of the methods developed for each of the four topics (model consolidation, primal method, branching strategy and cutting planes) within the branch-and-cut procedure. We present computational results for different types of lattices, where we both consider known benchmark instances from literature and random instances.

The protein folding problem attempts to predict the native, or folded, state of a protein in three-dimensional space, given its primary sequence of amino acids. One common approach for a solution is to treat each complex amino acid as a single sphere, or united atom, and to model each peptide linkage between residues by a virtual bond between spheres. Computational efforts being examined rely on two major assumptions: for any specific molecular conformation, a corresponding potential energy function can be computed, and the three-dimensional, folded state corresponds to the global minimum of this energy function. The optimization method being used to minimize the potential energy involves collecting a large number of conformers, each attained by finding a local minimum of the potential energy function from a random starting point. The information from these conformers is then used to form a convex quadratic global underestimating function for the potential energy of the known conformers. The minimum of this underestimator is used to predict the global minimum for the function, allowing a localized conformer search to be performed based on the predicted minimum. The new set of conformers generated by the localized search can serve as the basis for another quadratic underestimation. After several repetitions, the global minimum can be found with reasonable assurance. The conformer which lies at the global minimum represents the three-dimensional folded state of the molecule -- Author abstract.

The book will discuss classes of proteins and their folding, as well as the involvement of bioinformatics in solving the protein folding problem. In vivo and in vitro folding mechanisms are examined, as well as the failures of in vitro folding, a mechanism helpful in understanding disease caused by misfolding. The role of energy landscapes is also discussed and the computational approaches to these landscapes.

Proteins in living systems carry out a great variety of specific functions, each of which depends on the precise three-dimensional structure of a particular protein. Proteins are synthesized in the form of a flexible polypeptide chain that is capable of assuming a vast number of configurations; the transformation of this chain into a specific, relatively rigid three-dimensional structure is called folding--a remarkable process of self-organization. It is known that the amino acid sequences of some proteins have sufficient information to determine their three-dimensional structures. There are other proteins whose folding requires additional information beyond that found in the sequence of the mature protein. This book introduces the central problem of folding mechanisms as well as a number of other closely related issues. This book is neither a textbook nor a treatise. Rather, it is an attempt by several investigators to convey the excitement and challenges of those aspects of the folding problem in which they are actively engaged. The contributors give brief introductions to protein folding from the perspectives of molecular architecture, stability and dynamics, phage genetics, DNA exons, general physiology, and natural selection. They point out emerging new directions, including the suggestion of a class of diseases that result from protein folding defects.

Protein Physics: A Course of Lectures covers the most general problems of protein structure, folding and function. It describes key experimental facts and introduces concepts and theories, dealing with fibrous, membrane, and water-soluble globular proteins, in both their native and denatured states. The book systematically summarizes and presents the results of several decades of worldwide fundamental research on protein physics, structure, and folding, describing many physical models that help readers make estimates and predictions of physical processes that occur in proteins. New to this revised edition is the inclusion of novel information on amyloid aggregation, natively disordered proteins, protein folding in vivo, protein motors, misfolding, chameleon proteins, advances in protein engineering & design, and advances in the modeling of protein folding. Further, the book provides problems with solutions, many new and updated references, and physical and mathematical appendices. In addition, new figures (including stereo drawings, with a special appendix showing how to use them) are added, making this an ideal resource for graduate and advanced undergraduate students and researchers in academia in the fields of biophysics, physics, biochemistry, biologists, biotechnology, and chemistry. Fully revised and expanded new edition based on the latest research developments in protein physics Written by the world's top expert in the field Deals with fibrous, membrane, and water-soluble globular proteins, in both their native and denatured states Summarizes, in a systematic form, the results of several decades of worldwide fundamental research on protein physics and their structure and folding Examines experimental data on protein structure in the post-genome era

Utilizing high speed computational methods to extrapolate to the rest of the protein universe, the knowledge accumulated on a subset of examples, protein bioinformatics seeks to accomplish what was impossible before its invention, namely the assignment of functions or functional hypotheses for all known proteins.The Ten Most Wanted Solutions in Pro