DETERMINATION OF ORIENTATION AND POSITION OF MYOGLOBIN MOLECULE IN CRYSTAL OF SEAL MYOGLOBIN

The orientation of the myoglobin molecule in the crystal of seal myoglobin has been determined, by using the rotation function (Rossmann & Blow, 1962) to compare the 5.8 Å resolution data from sperm whale myoglobin with the 5 Å data from seal myoglobin obtained by Scouloudi (1969). The position of the molecule in the unit cell has been found using the Q-functions defined by Tollin (1966a). The position of the haem group obtained in this way is in good agreement with that obtained by Scouloudi (1969) from a 5 Å resolution electron density map obtained using the isomorphous replacement map. A three-dimensional electron density map has been obtained by calculating phases for a whale myoglobin molecule correctly located in the seal myoglobin cell and applying these to the observed seal structure amplitudes. This map has been compared with Scouloudi's published results and indicates a good agreement between the two investigations. © 1969.