NMR Structural Studies of Iron-Sulfur Proteins BRIAN J. GOODFELLOW*t and ANJOS L. MACEDO' 'Departamento de Quimica, Faculdade de Ci2ncias e Tecnologia, Universidade Nova de Lisboa, and ?Departamento de Quimica, Universidade del Aveiro, Aveiro, Portugal 1. Introduction 2. Iron-sulfur proteins 3. Paramagnetism and NMR 3.1. Electron-nuclear coupling 3.2. Nuclear relaxation 3.3. The nuclear Overhauser enhancement 4. NMR experiments for spin assignment 5. Structure calculation from NMR data 5.1. Distance constraints 5.2, Methods for structure calculations 5.3. Including the metal centre in structural calculations 6.1. Rubredoxin-type proteins 6.2. 2Fe ferredoxins 6.3. 3Fe ferredoxins 6.4. 4Fe proteins 6. NMR structural studies of iron-sulfur proteins 6.4.1. Ferredoxins 6.4.2. High-potential iron proteins 6.5. 7Fe and 8Fe ferredoxins Acknowledgements Note added in proof References 7. Conclusions 119 120 122 123 125 127 128 130 130 132 133 134 134 141 148 151 151 156 163 168 172 172 172 The use of N M R spectroscopy in the structural study of iron-sulfur proteins is reviewed. Some introductory theory of the electron-nucleus interaction and how it affects NMR parameters such as chemical shift and relaxation times is presented. Problems encountered in the determination of the solution structure of paramagnetic proteins are discussed and recent work in the field is extensively reviewed. 1. INTRODUCTION Since the mid-l980s, when the first protein structure in solution was deter- mined by NMR,' the area has seen an almost exponential growth. Nowadays ANNUAL REPORTS ON NMR SPECTROSCOPY VOLW 37 ISBN 0-12-505337-1 Copyright 0 19w Academic Press Limited All rights ofreproduction in any form reserved