Determination of the three-dimensional structure of toxins by protein crystallography

Protein crystallography has significantly contributed to the development of many areas of biochemical research, particularly in the understanding of p henomena related to molecular recognition. Examples include the formation o f enzyme-substrate complexes (and their subsequent catalysis), host cell in vasion by viruses, antigen neutralization and peptide display by proteins o f the immune system and many others. More recently, protein crystallography has also proved to be of great value in unraveling the molecular basis of many diseases as well as in the development of new drugs for their treatmen t. The X-ray diffraction technique in the elucidation of macromolecular str uctures is situated at the interface between the traditional research field s of biology, biochemistry, chemistry and physics where researchers are uni ted by a common interest in the detailed understanding of macromolecule fun ction and its relationship to three-dimensional structure. The purpose of t his review is to describe, without resort to mathematical detail, all of th e necessary steps for the complete determination of a three-dimensionaI str ucture by X-ray diffraction techniques. The basic procedures used for prote in isolation and crystallization, crystallographic data collection and anal ysis and, finally, structure determination and refinement are all briefly r eviewed. As such our efforts are not directed towards the specialist. Rathe r, it is our hope that the information presented will aid interested reader s from other fields in the understanding of more specialized literature and who may wish to employ the information contained therein in the planning o f their biological research. We hope that in so doing we will make clear bo th the power and limitations of the technique. (C) 2000 Elsevier Science Lt d. All rights reserved.