3-DIMENSIONAL STRUCTURE OF CATALASE FROM MICROCOCCUS-LYSODEIKTICUS AT 1.5 A RESOLUTION

The three-dimensional crystal structure of catalase from Micrococcus lysodeikticus has been solved by multiple isomorphous replacement and refined at 1.5 angstrom resolution. The subunit of the tetrameric molecule of 222 symmetry consists of a single polypeptide chain of about 500 amino acid residues and one haem group. The crystals belong to space group P4(2)2(1)2 with unit cell parameters a = b = 106.7 angstrom, c = 106.3 angstrom, and there is one subunit of the tetramer per asymmetric unit. The amino acid sequence has been tentatively determined by computer graphics model building and comparison with the known three-dimensional structure of beef liver catalase and sequences of several other catalases. The atomic model has been refined by Hendrickson and Konnert's least-squares minimisation against 94,315 reflections between 8 angstrom and 1.5 angstrom. The final model consists of 3,977 non-hydrogen atoms of the protein and haem group, 426 water molecules and one sulphate ion. The secondary and tertiary structures of the bacterial catalase have been analyzed and a comparison with the structure of beef liver catalase has been made.