Crystal structure of ferric Aplysia limacina myoglobin at 2 X 0 A resolution

The three-dimensional structure of ferric myoglobin from the mollusc Aplysia limacina has been refined at 2 X 0 A resolution. The crystallographic R factor, calculated at this stage, is 0 X 194. Despite its high content of apolar residues (both aromatic and aliphatic), Aplysia limacina myoglobin, which contains only one histidine residue (at the proximal position), has a structure that conforms to the common eight-helices globin fold observed in other phyla.