Fiber Diffraction from Macromolecular Assemblies

点击翻译按钮获取中文摘要

9630787 Makowski The long term goal of this project is to develop reliable methods for extracting structural information from fiber diffraction data and to use these methods to characterized the structure and activity of maromolecular assemblies. The ratio of data-to-model parameters for fiber diffraction is substantially lower than for x-ray crystallography, and even when a number of isomorphous derivatives are available, it may not be possible to obtain a unique structural solution from fiber diffraction data. Consequently, after a number of years, there continues to be substantial controversy in the literature about the structure of the filamentous bacteriophages M13 and Pf1. Differences among the molecular models for the viruses have substantial implications for our understanding of their membrane-mediated assembly, and for their use in phage display technology. Recent developments provide substantial hope that these controversies can be resolved in the near future: (i) It is now possible to obtain fiber diffraction data from structural variants of filamentous bacteriophages that can provide rigorous tests of competing structural models. (ii) A number of computational tests have recently been developed to assess the accuracy with which a molecular model of a crystalline protein has been constructed. These tests have been demonstrated for globular proteins and can now be utilized for analysis of structures of macromolecular assemblies. The principle goal of this project is to utilize these strategies to resolve the controversies about the structure of filamentous bacteriophages and to establish the use of these techniques for other systems to be studies by fiber diffraction. %%% The macromolecular assemblies that constitute a large part of any living system are far less amenable to structural characterization than soluble macromolecules, but information about their three-dimensional structure is central to understanding many biological processes at the molecular level. Few membran e proteins, filamentous proteins or large macromolecular assemblies have been solved to atomic resolution. Acquisition of structural information is the rate limiting step in our efforts to answer many fundamental questions about living systems: How are living structures assembled and how do the constituent molecules move in carrying out their vital functions? Answers to these questions require a detailed characterization of the role of macromolecule assemblies in the organization and activities of cellular systems. There are, as of yet, no routine procedures for determining the three-dimensional structures of these systems. The human imagination is such that a three-dimensional picture is really essential for an understanding of the function of a complex molecular machine. Fiber diffraction is one of the few techniques that can provide atomic or near-atomic resolution information about the structure of these systems. There are currently very few scientists using fiber diffraction in this country, and much of the future progress is likely to come from Europe and Japan. This program seeks to maintain state-of-the-art research in fiber diffraction in this country, and to improve the techniques in order to facilitate in the characterization of these system. ***