3-DIMENSIONAL STRUCTURE OF SERRATIA-MARCESCENS NUCLEASE AT 1.7 ANGSTROM RESOLUTION AND MECHANISM OF ITS ACTION

The three-dimensional crystal structure of Serratia marcescens (Sm) nu clease has been refined at 1.7 Angstrom resolution to the R-factor of 17.3% and R-free of 22.2%. The final model consists of 3678 non-hydrog en atoms and 443 water molecules. The analysis of the secondary and th e tertiary structures of the Sm nuclease suggests a topology which rev eals essential inner symmetry in all the three layers forming the mono mer. We propose the plausible mechanism of its action based on a conce rted participation of the catalytically important amino acid residues of the enzyme active site. (C) 1997 Federation of European Biochemical Societies.