The conference entitled "The Translational Apparatus" was held in Berlin from October 31 to November 5, 1992, in honorem et memoriam of H. G. Wittmann. The presentations of the rewarding, enjoyable and scientifically exciting week in Berlin were a fitting appreciation of this great man, and all participants and speakers contributed to the success of the meeting. The second reason for holding the Berlin meeting was to convene a group of scientists for a state-of-the-art presentation on ribosomes and related subjects; the outcome is this book. We have broadened the spectrum of topics to cover activities preceding and following pure ribosomal functions, such as "Synthetases" and "Protein Sorting", respectively, and we took the liberty of ordering the contributions in a way which does not always reflect the order of speakers. We are grateful to the authors who patiently tolerated our organization and our regulations for manuscripts. K.H. Nierhaus F. Franceschi A.R. Subramanian v CONTENTS I. tRNA and Aminoaeyl-tRNA Synthetases 1. The Crystal Structure of SeryI-tRNA Synthetase and its Complexes with A TP and tRNASer................................................................................................................. 1 S. Cusack, C. Berthet-Colominas, V. Biou, F. Borel, M. Fujinaga, M. Hartlein, I.